Organometallic compound and organic light-emitting device including the same

ABSTRACT

An organometallic compound represented by Formula 1: 
       M(L 1 ) n1 (L 2 ) n2   Formula 1
         wherein in Formula 1, M, L 1 , L 2 , n1, and n2 are the same as described in the specification.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority to and the benefit of Korean PatentApplication No. 10-2015-0017475, filed on Feb. 4, 2015, in the KoreanIntellectual Property Office, the disclosure of which is incorporatedherein in its entirety by reference.

BACKGROUND

1. Field

The present disclosure relates to an organometallic compound and anorganic light-emitting device including the same.

2. Description of the Related Art

Organic light emitting devices (OLEDs) are self-emission devices thathave wide viewing angles, high contrast ratios, and short responsetimes. In addition, OLEDs exhibit excellent brightness, driving voltage,and response speed characteristics, and produce full-color images.

A typical organic light-emitting device includes an anode, a cathode,and an organic layer that is disposed between the anode and the cathodeand includes an emission layer. A hole transport region may be disposedbetween the anode and the emission layer, and an electron transportregion may be disposed between the emission layer and the cathode. Holesprovided from the anode may move toward the emission layer through thehole transport region, and electrons provided from the cathode may movetoward the emission layer through the electron transport region. Theholes and the electrons are recombined in the emission layer to produceexcitons. These excitons change from an excited state to a ground state,thereby generating light.

Various types of organic light emitting devices are known. However,there still remains a need in OLEDs having low driving voltage, highefficiency, high brightness, and long lifespan.

SUMMARY

One or more embodiments relate to a novel organometallic compound and anorganic light-emitting device including the same.

Additional aspects will be set forth in part in the description whichfollows and, in part, will be apparent from the description, or may belearned by practice of the presented exemplary embodiments.

Provided is an organometallic compound represented by Formula 1:

M in Formula 1 may be selected from Ir, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm,and Rh,

-   -   L₁ in Formula 1 is selected from ligands represented by Formula        2A, and n1 is 1, 2 or 3, and when n1 is 2 or greater, two or        more groups L₁ may be identical to or different from each other,    -   L₂ in Formula 1 may be selected from a monovalent organic        ligand, a divalent organic ligand, a trivalent organic ligand,        and a tetravalent organic ligand, and n2 is 0, 1, 2, 3 or 4, and        when n2 is 2 or greater, two or more L₂(s) may be identical to        or different from each other,    -   L₁ and L₂ in Formula 1 may be different from each other,    -   R₁, R₂ and R₁₁ to R₁₅ in Formula 2A may be each independently        selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, —SF₅, a        hydroxyl group, a cyano group, a nitro group, an amino group, an        amidino group, a hydrazine group, a hydrazone group, a        carboxylic acid group or a salt thereof, a sulfonic acid group        or a salt thereof, a phosphoric acid group or a salt thereof, a        substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted        or unsubstituted C₂-C₆₀ alkenyl group, a substituted or        unsubstituted C₂-C₆₀ alkynyl group, a substituted or        unsubstituted C₁-C₆₀ alkoxy group, a substituted or        unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or        unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or        unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted        C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀        arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl        group, a substituted or unsubstituted monovalent non-aromatic        condensed polycyclic group, a substituted or unsubstituted        monovalent non-aromatic condensed heteropolycyclic group,        —N(Q₁)(Q₂), and —B(Q₃)(Q₄),    -   provided that at least one selected from R₁₁ to R₁₄ in Formula        2A is not a hydrogen,    -   b1 in Formula 2A is selected from 1, 2, 3, and 4, and    -   b2 is selected from 0, 1, 2, and 3,    -   each of * and *′ in Formula 2A indicates a binding site to M in        Formula 1, and    -   at least one of substituents of the substituted C₁-C₆₀ alkyl        group, substituted C₂-C₆₀ alkenyl group, substituted C₂-C₆₀        alkynyl group, substituted C₁-C₆₀ alkoxy group, substituted        C₃-C₁₀ cycloalkyl group, substituted C₁-C₁₀ heterocycloalkyl        group, substituted C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀        heterocycloalkenyl group, substituted C₆-C₆₀ aryl group,        substituted C₆-C₆₀ aryloxy group, substituted C₆-C₆₀ arylthio        group, substituted C₁-C₆₀ heteroaryl group, substituted        monovalent non-aromatic condensed polycyclic group and        substituted monovalent non-aromatic condensed heteropolycyclic        group may be selected from:    -   a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,        —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino        group, an amidino group, a hydrazine group, a hydrazone group, a        carboxylic acid group or a salt thereof, a sulfonic acid group        or a salt thereof, a phosphoric acid group or a salt thereof, a        C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl        group, and a C₁-C₆₀ alkoxy group;    -   a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl        group, and a C₁-C₆₀ alkoxy group, each substituted with at least        one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid group or a salt thereof, a phosphoric        acid group or a salt thereof, a C₃-C₁₀ cycloalkyl group, a        C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a        C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀        aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl        group, a monovalent non-aromatic condensed polycyclic group, a        monovalent non-aromatic condensed heteropolycyclic group,        —N(Q₁₁)(Q₁₂), and —B(Q₁₃)(Q₁₄);    -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a        C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a        C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio        group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic        condensed polycyclic group, and a monovalent non-aromatic        condensed heteropolycyclic group;    -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a        C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a        C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio        group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic        condensed polycyclic group, and a monovalent non-aromatic        condensed heteropolycyclic group, each substituted with at least        one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid group or a salt thereof, a phosphoric        acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀        alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a        C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a        C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a        C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio        group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic        condensed polycyclic group, a monovalent non-aromatic condensed        heteropolycyclic group, —N(Q₂₁)(Q₂₂), and —B(Q₂₃)(Q₂₄); and    -   —N(Q₃₁)(Q₃₂) and —B(Q₃₃)(Q₃₄),    -   wherein Q₁ to Q₄, Q₁₁ to Q₁₄, Q₂₁ to Q₂₄, and Q₃₁ to Q₃₄ are        each independently selected from a hydrogen, a deuterium, —F,        —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an        amino group, an amidino group, a hydrazine group, a hydrazone        group, a carboxylic acid group or a salt thereof, a sulfonic        acid group or a salt thereof, a phosphoric acid group or a salt        thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a        substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted        or unsubstituted C₂-C₆₀ alkynyl group, a substituted or        unsubstituted C₁-C₆₀ alkoxy group, a substituted or        unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or        unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or        unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted        C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀        arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl        group, a substituted or unsubstituted monovalent non-aromatic        condensed polycyclic group, and a substituted or unsubstituted        monovalent non-aromatic condensed heteropolycyclic group.

Another aspect provides an organic light-emitting device including:

-   -   a first electrode;    -   a second electrode; and    -   an organic layer disposed between the first electrode and the        second electrode,    -   wherein the organic layer includes an emission layer and at        least one organometallic compound represented by Formula 1.

The emission layer may include the organometallic compound.

The organometallic compound included in the emission layer may act as adopant, and the emission layer may further include a host.

BRIEF DESCRIPTION OF THE DRAWINGS

These and/or other aspects will become apparent and more readilyappreciated from the following description of the exemplary embodiments,taken in conjunction with the accompanying drawings in which: FIG. 1 isa schematic view of an organic light-emitting device according to anembodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to exemplary embodiments, examplesof which are illustrated in the accompanying drawings, wherein likereference numerals refer to like elements throughout. In this regard,the present exemplary embodiments may have different forms and shouldnot be construed as being limited to the descriptions set forth herein.Accordingly, the exemplary embodiments are merely described below, byreferring to the figures, to explain aspects of the present disclosure.As used herein, the term “and/or” includes any and all combinations ofone or more of the associated listed items. Expressions such as “atleast one of,” when preceding a list of elements, modify the entire listof elements and do not modify the individual elements of the list.

It will be understood that when an element is referred to as being “on”another element, it can be directly in contact with the other element orintervening elements may be present therebetween. In contrast, when anelement is referred to as being “directly on” another element, there areno intervening elements present.

It will be understood that, although the terms first, second, third etc.may be used herein to describe various elements, components, regions,layers, and/or sections, these elements, components, regions, layers,and/or sections should not be limited by these terms. These terms areonly used to distinguish one element, component, region, layer, orsection from another element, component, region, layer, or section.Thus, a first element, component, region, layer, or section discussedbelow could be termed a second element, component, region, layer, orsection without departing from the teachings of the present embodiments.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting. As used herein, thesingular forms “a,” “an,” and “the” are intended to include the pluralforms as well, unless the context clearly indicates otherwise.

It will be further understood that the terms “comprises” and/or“comprising,” or “includes” and/or “including” when used in thisspecification, specify the presence of stated features, regions,integers, steps, operations, elements, and/or components, but do notpreclude the presence or addition of one or more other features,regions, integers, steps, operations, elements, components, and/orgroups thereof.

Spatially relative terms, such as “beneath,” “below,” “lower,” “above,”“upper” and the like, may be used herein for ease of description todescribe one element or feature's relationship to another element(s) orfeature(s) as illustrated in the figures. It will be understood that thespatially relative terms are intended to encompass differentorientations of the device in use or operation in addition to theorientation depicted in the figures. For example, if the device in thefigures is turned over, elements described as “below” or “beneath” otherelements or features would then be oriented “above” the other elementsor features. Thus, the exemplary term “below” can encompass both anorientation of above and below. The device may be otherwise oriented(rotated 90 degrees or at other orientations) and the spatially relativedescriptors used herein interpreted accordingly.

About” or “approximately” as used herein is inclusive of the statedvalue and means within an acceptable range of deviation for theparticular value as determined by one of ordinary skill in the art,considering the measurement in question and the error associated withmeasurement of the particular quantity (i.e., the limitations of themeasurement system). For example, “about” can mean within one or morestandard deviations, or within ±30%, 20%, 10%, 5% of the stated value.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art and thepresent disclosure, and will not be interpreted in an idealized oroverly formal sense unless expressly so defined herein.

Exemplary embodiments are described herein with reference to crosssection illustrations that are schematic illustrations of idealizedembodiments. As such, variations from the shapes of the illustrations asa result, for example, of manufacturing techniques and/or tolerances,are to be expected. Thus, embodiments described herein should not beconstrued as limited to the particular shapes of regions as illustratedherein but are to include deviations in shapes that result, for example,from manufacturing. For example, a region illustrated or described asflat may, typically, have rough and/or nonlinear features. Moreover,sharp angles that are illustrated may be rounded. Thus, the regionsillustrated in the figures are schematic in nature and their shapes arenot intended to illustrate the precise shape of a region and are notintended to limit the scope of the present claims.

An organometallic compound according to an exemplary embodiment isrepresented by Formula 1:

M(L₁)_(n1)(L₂)_(n2).  Formula 1

M in Formula 1 may be selected from iridium (Ir), platinum (Pt), osmium(Os), titanium (Ti), zirconium (Zr), hafnium (Hf), europium (Eu),terbium (Tb), thulium (Tm), and rhodium (Rh),

For example, M in Formula 1 may be selected from iridium, platinum,osmium, and rhodium.

In an embodiment, M in Formula 1 may be selected from iridium andplatinum, but is not limited thereto.

L₁ in Formula 1 is selected from ligands represented by Formula 2A. n1in Formula 1 indicates the number of groups L₁, and n1 may be 1, 2, or3. When n1 is 2 or greater, two or more groups L₁ may be identical to ordifferent from each other.

L₂ in Formula 1 may be selected from a monovalent organic ligand, adivalent organic ligand, a trivalent organic ligand, and a tetravalentorganic ligand, n2 may be 0, 1, 2, 3, or 4, when n2 is 2 or greater, twoor more groups L₂ may be identical to or different from each other.

L₁ and L₂ in Formula 1 may be different from each other.

For example, n1 in Formula 1 may be 1, but is not limited thereto.

In some embodiments, the organometallic compound represented by Formula1 is not in the form of a salt consisting of an ionic pair, and may beneutral.

In an embodiment, regarding Formula 1, M may be Ir and the sum of n1 andn2 may be 3; or M may be Pt and the sum of n1 and n2 may be 2, and theorganometallic compound represented by Formula 1 may not be in the formof a salt consisting of an ionic pair, and may be neutral.

R₁, R₂, and R₁₁ to R₁₅ in Formula 2A may be each independently selectedfrom a hydrogen, a deuterium, —F, —Cl, —Br, —I, —SF₅, a hydroxyl group,a cyano group, a nitro group, an amino group, an amidino group, ahydrazine group, a hydrazone group, a carboxylic acid group or a saltthereof, a sulfonic acid group or a salt thereof, a phosphoric acidgroup or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkylgroup, a substituted or unsubstituted C₂-C₆₀ alkenyl group, asubstituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted orunsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkylgroup, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, asubstituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, asubstituted or unsubstituted C₆-C₆₀ aryl group, a substituted orunsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstitutedC₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroarylgroup, a substituted or unsubstituted monovalent non-aromatic condensedpolycyclic group, a substituted or unsubstituted monovalent non-aromaticcondensed heteropolycyclic group, —N(Q₁)(Q₂), and —B(Q₃)(Q₄), providedthat at least one selected from R₁₁ to R₁₄ in Formula 2A may not be ahydrogen.

For example, R₁ and R₂ in Formula 2A may be each independently selectedfrom

-   -   a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a        cycloheptyl group, a cyclooctyl group, an adamantanyl        (adamantyl) group, a norbornanyl (norbornyl) group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, an        imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl        group; and a C₁-C₁₀ alkyl group, a cyclopentyl group, a        cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an        adamantanyl group, a norbornanyl group, a cyclopentenyl group, a        cyclohexenyl group, a cycloheptenyl group, a phenyl group, a        naphthyl group, a fluorenyl group, a phenanthrenyl group, an        anthracenyl group, a fluoranthenyl group, a triphenylenyl group,        a pyrenyl group, a chrysenyl group, a pyrrolyl group, a        thiophenyl group, a furanyl group, an imidazolyl group, a        pyrazolyl group, a thiazolyl group, an isothiazolyl group, an        oxazolyl group, an isoxazolyl group, a pyridinyl group, a        pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an        isoindolyl group, an indolyl group, an indazolyl group, a        purinyl group, a quinolinyl group, an isoquinolinyl group, a        benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl        group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl        group, a benzoimidazolyl group, a benzofuranyl group, a        benzothiophenyl group, an isobenzothiazolyl group, a        benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group,        a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a        dibenzofuranyl group, a dibenzothiophenyl group, a        benzocarbazolyl group, a dibenzocarbazolyl group, an        imidazopyridinyl group, an imidazopyrimidinyl group, and        1,2,3,4-tetrahydronaphthyl group, each substituted with at least        one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid group or a salt thereof, a phosphoric        acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C_(r) C₂₀        alkoxy group, a cyclopentyl group, a cyclohexyl group, a        cycloheptyl group, a cyclooctyl group, an adamantanyl group, a        norbornanyl group, a cyclopentenyl group, a cyclohexenyl group,        a cycloheptenyl group, a phenyl group, a naphthyl group, a        fluorenyl group, a phenanthrenyl group, an anthracenyl group, a        fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a        chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl        group, an imidazolyl group, a pyrazolyl group, a thiazolyl        group, an isothiazolyl group, an oxazolyl group, an isoxazolyl        group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl        group, a pyridazinyl group, an isoindolyl group, an indolyl        group, an indazolyl group, a purinyl group, a quinolinyl group,        an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group.

In an embodiment, R₁ and R₂ in Formula 2A may be each independentlyselected from

-   -   a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a        fluorenyl group, a phenanthrenyl group, an anthracenyl group, a        fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a        chrysenyl group, a pyridinyl group, a pyrazinyl group, a        pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a carbazolyl group, a        phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl        group, a benzothiophenyl group, an isobenzothiazolyl group, a        benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group,        a dibenzofuranyl group, a dibenzothiophenyl group, a        benzocarbazolyl group, a dibenzocarbazolyl group, an        imidazopyridinyl group, an imidazopyrimidinyl group, and a        1,2,3,4-tetrahydronaphthyl group; and    -   a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a        fluorenyl group, a phenanthrenyl group, an anthracenyl group, a        fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a        chrysenyl group, a pyridinyl group, a pyrazinyl group, a        pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a carbazolyl group, a        phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl        group, a benzothiophenyl group, an isobenzothiazolyl group, a        benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group,        a dibenzofuranyl group, a dibenzothiophenyl group, a        benzocarbazolyl group, a dibenzocarbazolyl group, an        imidazopyridinyl group, an imidazopyrimidinyl group, and a        1,2,3,4-tetrahydronaphthyl group, each substituted with at least        one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid group or a salt thereof, a phosphoric        acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀        alkoxy group, a phenyl group, a naphthyl group, a fluorenyl        group, a phenanthrenyl group, an anthracenyl group, a        fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a        chrysenyl group, a pyridinyl group, a pyrazinyl group, a        pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a carbazolyl group, a        phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl        group, a benzothiophenyl group, an isobenzothiazolyl group, a        benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group,        a dibenzofuranyl group, a dibenzothiophenyl group, a        benzocarbazolyl group, a dibenzocarbazolyl group, an        imidazopyridinyl group, and an imidazopyrimidinyl group.

In some embodiments, R₁ and R₂ in Formula 2A may be each independentlyselected from

-   -   a phenyl group, a naphthyl group, a pyridinyl group, a        pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a        quinoxalinyl group, a quinazolinyl group, a carbazolyl group,        and a 1,2,3,4-tetrahydronaphthyl group; and    -   a phenyl group, a naphthyl group, a pyridinyl group, a        pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a        quinoxalinyl group, a quinazolinyl group, a carbazolyl group,        and a 1,2,3,4-tetrahydronaphthyl group, each substituted with at        least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃,        —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano        group, a nitro group, an amino group, an amidino group, a        hydrazine group, a hydrazone group, a carboxylic acid group or a        salt thereof, a sulfonic acid group or a salt thereof, a        phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a        C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a        pyridinyl group, a pyrimidinyl group, a quinolinyl group, an        isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group,        and a carbazolyl group.

For example, R₁ and R₂ in Formula 2A may be identical to or differentfrom each other. In an embodiment, R₁ and R₂ in Formula 2A may beidentical to each other.

In an embodiment, R₁ and R₂ in Formula 2A may be identical to eachother, R₁ and R₂ may be selected from a phenyl group; and a phenyl groupsubstituted with at least one C₁-C₁₀ alkyl group.

R₁₁ to R₁₅ in Formula 2A may be each independently selected from

-   -   a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a        cyano group, a nitro group, an amino group, an amidino group, a        hydrazine group, a hydrazone group, a carboxylic acid group or a        salt thereof, a sulfonic acid group or a salt thereof, a        phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl        group, and a C₁-C₂₀ alkoxy group;    -   a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted        with at least one selected from a deuterium, —F, —Cl, —Br, —I,        —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a        cyano group, a nitro group, an amino group, an amidino group, a        hydrazine group, a hydrazone group, a carboxylic acid group or a        salt thereof, a sulfonic acid group or a salt thereof, a        phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a        cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a pyridinyl group, and        a pyrimidinyl group;    -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group;    -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group, each substituted with at least one        selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂,        —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro        group, an amino group, an amidino group, a hydrazine group, a        hydrazone group, a carboxylic acid group or a salt thereof, a        sulfonic acid group or a salt thereof, a phosphoric acid group        or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group,        a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group; and    -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),    -   wherein Q₁ to Q₄ may be each independently selected from    -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,        —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and        —CD₂CDH₂;    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group; and    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group, each        substituted with at least one selected from a deuterium, a        C₁-C₁₀ alkyl group, and a phenyl group.

For example, R₁₁ to R₁₅ in Formula 2A may be each independently selectedfrom

-   -   a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅,        a methyl group, an ethyl group, an n-propyl group, an isopropyl        group, an n-butyl group, an isobutyl group, a sec-butyl group, a        tert-butyl group, an n-pentyl group, an isopentyl group, a        sec-pentyl group, a tert-pentyl group, an n-hexyl group, an        iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an        n-heptyl group, an iso-heptyl group, a sec-heptyl group, a        tert-heptyl group, an n-octyl group, an iso-octyl group, a        sec-octyl group, a tert-octyl group, an n-nonyl group, an        iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an        n-decyl group, an iso-decyl group, a sec-decyl group, a        tert-decyl group, a methoxy group, an ethoxy group, a propoxy        group, butoxy group, a pentoxy group, a cyclopentyl group, a        cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an        adamantanyl group, a norbornanyl group, a cyclopentenyl group, a        cyclohexenyl group, a cycloheptenyl group, a phenyl group, a        naphthyl group, a pyridinyl group, and a pyrimidinyl group;    -   a methyl group, an ethyl group, an n-propyl group, an isopropyl        group, an n-butyl group, an isobutyl group, a sec-butyl group, a        tert-butyl group, an n-pentyl group, an isopentyl group, a        sec-pentyl group, a tert-pentyl group, an n-hexyl group, an        iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an        n-heptyl group, an iso-heptyl group, a sec-heptyl group, a        tert-heptyl group, an n-octyl group, an iso-octyl group, a        sec-octyl group, a tert-octyl group, an n-nonyl group, an        iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an        n-decyl group, an iso-decyl group, a sec-decyl group, a        tert-decyl group, a methoxy group, an ethoxy group, a propoxy        group, butoxy group, a pentoxy group, a cyclopentyl group, a        cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an        adamantanyl group, a norbornanyl group, a cyclopentenyl group, a        cyclohexenyl group, a cycloheptenyl group, a phenyl group, a        naphthyl group, a pyridinyl group, and a pyrimidinyl group, each        substituted with at least one selected from a deuterium, —F,        —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro        group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a        cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a pyridinyl group, and        a pyrimidinyl group; and    -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),    -   wherein Q₁ to Q₄ may be each independently selected from    -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,        —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and        —CD₂CDH₂;    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group and a naphthyl group; and    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group, each        substituted with at least one selected from a deuterium, a        C₁-C₁₀ alkyl group, and a phenyl group.

In an embodiment, R₁₁ to R₁₅ in Formula 2A may be each independentlyselected from a hydrogen, a deuterium, —F, a cyano group, a nitro group,—SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups representedby Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to10-28,

-   -   R₁ and R₂ in Formula 2A may be each independently selected from    -   a phenyl group, a naphthyl group, a pyridinyl group, a        pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a        quinoxalinyl group, a quinazolinyl group, and a carbazolyl        group; and    -   a phenyl group, a naphthyl group, a pyridinyl group, a        pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a        quinoxalinyl group, a quinazolinyl group, and a carbazolyl        group, each substituted with at least one selected from a        deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,        —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino        group, an amidino group, a hydrazine group, a hydrazone group, a        carboxylic acid group or a salt thereof, a sulfonic acid group        or a salt thereof, a phosphoric acid group or a salt thereof, a        C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a        naphthyl group, a pyridinyl group, a pyrimidinyl group, a        quinolinyl group, an isoquinolinyl group, a quinoxalinyl group,        a quinazolinyl group, and a carbazolyl group, but are not        limited thereto:

In Formula 2A, b1 may be selected from 1, 2, 3, and 4, and b2 may beselected from 0, 1, 2, and 3.

For example, b1 in Formula 2A may be 1 or 2, for example, b1 in Formula2A may be 1, but is not limited thereto.

Each of* and *′ in Formula 2A indicates a binding site to M in Formula1.

In an embodiment, L₁ in Formula 1 may be selected from ligandsrepresented by Formulae 2A-1 to 2A-15:

Descriptions of R₁, R₂, R₁₁ to R₁₅, b1 and b2 in Formulae 2A-1 to 2A-15are the same as above, provided that each of R₁₁ to R₁₄ is not hydrogen.

For example, R₁₁ to R₁₄ in Formulae 2A-1 to 2A-15 may be eachindependently selected from

-   -   a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group,        a nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid group or a salt thereof, a phosphoric        acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl group, and a        C₁-C₂₀ alkoxy group;    -   a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted        with at least one selected from a deuterium, —F, —Cl, —Br, —I,        —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a        cyano group, a nitro group, an amino group, an amidino group, a        hydrazine group, a hydrazone group, a carboxylic acid group or a        salt thereof, a sulfonic acid group or a salt thereof, a        phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a        cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a pyridinyl group, and        a pyrimidinyl group;    -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group;    -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group, each substituted with at least one        selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂,        —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro        group, an amino group, an amidino group, a hydrazine group, a        hydrazone group, a carboxylic acid group or a salt thereof, a        sulfonic acid group or a salt thereof, a phosphoric acid group        or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group,        a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group; and    -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),    -   wherein Q₁ to Q₄ are each independently selected from    -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,        —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and        —CD₂CDH₂;    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group; and    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group, each        substituted with at least one selected from a deuterium, a        C₁-C₁₀ alkyl group, and a phenyl group.

In some embodiments, L₁ in Formula 1 may be selected from groupsrepresented by Formula 2A(1):

Descriptions of R₁, R₂ and R₁₁ to R₁₄ in Formula 2A(1) are the same asdescribed above, and descriptions of R_(15a), R_(15b), and R_(15c) arethe same as those provided in connection with R₁₅.

For example, L₁ in Formula 1 may be selected from ligands represented byFormulae 2A(1)-1 to 2A(1)-15:

Descriptions of R₁, R₂ and R₁₁ to R₁₄ in Formulae 2A(1)-1 to 2A(1)-15are the same as described above, provided that each of R₁₁ to R₁₄ is nothydrogen, and descriptions of R_(15a), R_(15b), and R_(15c) are the sameas those provided in connection with R₁₅.

For example, in Formulae 2A(1)-1 to 2A(1)-15,

-   -   R₁₁ to R₁₄ may be each independently selected from    -   a deuterium, —F, a cyano group, a nitro group, —SF₅, a methyl        group, an ethyl group, an n-propyl group, an isopropyl group, an        n-butyl group, an isobutyl group, a sec-butyl group, a        tert-butyl group, an n-pentyl group, an isopentyl group, a        sec-pentyl group, a tert-pentyl group, an n-hexyl group, an        iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an        n-heptyl group, an iso-heptyl group, a sec-heptyl group, a        tert-heptyl group, an n-octyl group, an iso-octyl group, a        sec-octyl group, a tert-octyl group, an n-nonyl group, an        iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an        n-decyl group, an iso-decyl group, a sec-decyl group, a        tert-decyl group, a methoxy group, an ethoxy group, a propoxy        group, butoxy group, a pentoxy group, a cyclopentyl group, a        cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an        adamantanyl group, a norbornanyl group, a cyclopentenyl group, a        cyclohexenyl group, a cycloheptenyl group, a phenyl group, a        naphthyl group, a pyridinyl group, and a pyrimidinyl group;    -   a methyl group, an ethyl group, an n-propyl group, an isopropyl        group, an n-butyl group, an isobutyl group, a sec-butyl group, a        tert-butyl group, an n-pentyl group, an isopentyl group, a        sec-pentyl group, a tert-pentyl group, an n-hexyl group, an        iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an        n-heptyl group, an iso-heptyl group, a sec-heptyl group, a        tert-heptyl group, an n-octyl group, an iso-octyl group, a        sec-octyl group, a tert-octyl group, an n-nonyl group, an        iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an        n-decyl group, an iso-decyl group, a sec-decyl group, a        tert-decyl group, a methoxy group, an ethoxy group, a propoxy        group, butoxy group, a pentoxy group, a cyclopentyl group, a        cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an        adamantanyl group, a norbornanyl group, a cyclopentenyl group, a        cyclohexenyl group, a cycloheptenyl group, a phenyl group, a        naphthyl group, a pyridinyl group, and a pyrimidinyl group, each        substituted with at least one selected from a deuterium, —F,        —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro        group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a        cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a pyridinyl group, and        a pyrimidinyl group; and    -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),    -   R_(15a), R_(15b), and R_(15c) may be each independently selected        from    -   a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅,        a methyl group, an ethyl group, an n-propyl group, an isopropyl        group, an n-butyl group, an isobutyl group, a sec-butyl group, a        tert-butyl group, an n-pentyl group, an isopentyl group, a        sec-pentyl group, a tert-pentyl group, an n-hexyl group, an        iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an        n-heptyl group, an iso-heptyl group, a sec-heptyl group, a        tert-heptyl group, an n-octyl group, an iso-octyl group, a        sec-octyl group, a tert-octyl group, an n-nonyl group, an        iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an        n-decyl group, an iso-decyl group, a sec-decyl group, a        tert-decyl group, a methoxy group, an ethoxy group, a propoxy        group, butoxy group, a pentoxy group, a cyclopentyl group, a        cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an        adamantanyl group, a norbornanyl group, a cyclopentenyl group, a        cyclohexenyl group, a cycloheptenyl group, a phenyl group, a        naphthyl group, a pyridinyl group, and a pyrimidinyl group;    -   a methyl group, an ethyl group, an n-propyl group, an isopropyl        group, an n-butyl group, an isobutyl group, a sec-butyl group, a        tert-butyl group, an n-pentyl group, an isopentyl group, a        sec-pentyl group, a tert-pentyl group, an n-hexyl group, an        iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an        n-heptyl group, an iso-heptyl group, a sec-heptyl group, a        tert-heptyl group, an n-octyl group, an iso-octyl group, a        sec-octyl group, a tert-octyl group, an n-nonyl group, an        iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an        n-decyl group, an iso-decyl group, a sec-decyl group, a        tert-decyl group, a methoxy group, an ethoxy group, a propoxy        group, butoxy group, a pentoxy group, a cyclopentyl group, a        cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an        adamantanyl group, a norbornanyl group, a cyclopentenyl group, a        cyclohexenyl group, a cycloheptenyl group, a phenyl group, a        naphthyl group, a pyridinyl group, and a pyrimidinyl group, each        substituted with at least one selected from a deuterium, —F,        —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro        group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a        cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a pyridinyl group, and        a pyrimidinyl group; and    -   —N(Q₁)(Q₂) and —B(Q₃)(Q₄),    -   R₁ and R₂ may be each independently selected from    -   a phenyl group, a naphthyl group, a pyridinyl group, a        pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a        quinoxalinyl group, a quinazolinyl group, and a carbazolyl        group; and    -   a phenyl group, a naphthyl group, a pyridinyl group, a        pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a        quinoxalinyl group, a quinazolinyl group, and a carbazolyl        group, each substituted with at least one selected from a        deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,        —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino        group, an amidino group, a hydrazine group, a hydrazone group, a        carboxylic acid group or a salt thereof, a sulfonic acid group        or a salt thereof, a phosphoric acid group or a salt thereof, a        C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a        naphthyl group, a pyridinyl group, a pyrimidinyl group, a        quinolinyl group, an isoquinolinyl group, a quinoxalinyl group,        a quinazolinyl group, and a carbazolyl group, and    -   Q₁ to Q₄ may be each independently selected from    -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,        —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H,        and—CD₂CDH₂;    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group; and    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group, each        substituted with at least one selected from a deuterium, a        C₁-C₁₀ alkyl group, and a phenyl group.

In some embodiments, in Formulae 2A(1)-1 to 2A(1)-15,

-   -   R₁₁ to R₁₄ may be each independently selected from a deuterium,        —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, groups represented by Formulae 9-1 to        9-17, and groups represented by Formulae 10-1 to 10-28,    -   R_(15a), R_(15b), and R_(15c) may be each independently selected        from a hydrogen, a deuterium, —F, a cyano group, a nitro group,        —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups        represented by Formulae 9-1 to 9-17, and groups represented by        Formulae 10-1 to 10-28,    -   R₁ and R₂ may be each independently selected from    -   a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a        pyridinyl group, a pyrimidinyl group, a quinolinyl group, an        isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group,        and a carbazolyl group; and    -   a phenyl group, a naphthyl group, a pyridinyl group, a        pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a        quinoxalinyl group, a quinazolinyl group, and a carbazolyl        group, each substituted with at least one selected from a        deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,        —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino        group, an amidino group, a hydrazine group, a hydrazone group, a        carboxylic acid group or a salt thereof, a sulfonic acid group        or a salt thereof, a phosphoric acid group or a salt thereof, a        C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a        naphthyl group, a pyridinyl group, a pyrimidinyl group, a        quinolinyl group, an isoquinolinyl group, a quinoxalinyl group,        a quinazolinyl group, and a carbazolyl group, but are not        limited thereto.

L₂ in Formula 1 may be selected from groups represented by Formulae 3Ato 3G:

In Formulae 3A to 3G,

-   -   Y₁₁ to Y₁₆ may be each independently a carbon (C) or a nitrogen        (N), Y₁₁ and Y₁₂ may be linked to each other via a single bond        or a double bond, Y₁₃ and Y₁₄ may be linked to each other via a        single bond or a double bond, Y₁₅ and Y₁₆ may be linked to each        other via a single bond or a double bond,    -   CY₃ to CY₅ may be each independently selected from a C₅-C₆₀        cyclic group and a C₂-C₆₀ heterocyclic group,    -   a1 to a3 may be each independently an integer of 1 to 5;    -   A₁ is P or As;    -   X_(11a), X_(11b), X_(12a), X_(12b), X_(13a), and X_(13b) may be        each independently selected from N, O, N(R₃₄), P(R₃₅)(R₃₆), and        As(R₃₇)(R₃₈) (provided that X_(12a), X_(12b), X_(13a), and        X_(13b) are neither N nor O);    -   R_(33″) and R_(34″) may be each independently selected from a        single bond, a double bond, a substituted or unsubstituted C₁-C₅        alkylene group, a substituted or unsubstituted C₂-C₅ alkenylene        group, and a substituted or unsubstituted C₆-C₁₀ arylene group;    -   Z₁ to Z₃, R₃₁, R_(32a), R_(32b), R_(32c), R_(33a), R_(33b), R₃₄        to R₃₈, R_(35a), R_(35b), R_(35c), and R_(35d) may be each        independently selected from a hydrogen, a deuterium, —F, —Cl,        —Br, —I, a hydroxyl group, a cyano group, a nitro group, an        amino group, an amidino group, a hydrazine group, a hydrazone        group, a carboxylic acid group or a salt thereof, a sulfonic        acid group or a salt thereof, a phosphoric acid group or a salt        thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a        substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted        or unsubstituted C₂-C₆₀ alkynyl group, a substituted or        unsubstituted C₁-C₆₀ alkoxy group, a substituted or        unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or        unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or        unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted        C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀        arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl        group, a substituted or unsubstituted monovalent non-aromatic        condensed polycyclic group, a substituted or unsubstituted        monovalent non-aromatic condensed heteropolycyclic group,        —N(Q₁)(Q₂), —B(Q₃)(Q₄), —Si(Q₅)(Q₆)(Q₇), and —P(═O)(Q₈)(Q₉),    -   each of * and *′ indicates a binding site to M in Formula 1, and    -   at least one of substituents of the substituted C₁-C₅ alkylene        group, substituted C₂-C₅ alkenylene group, substituted C₆-C₁₀        arylene group, substituted C₁-C₆₀ alkyl group, substituted        C₂-C₆₀ alkenyl group, substituted C₂-C₆₀ alkynyl group,        substituted C₁-C₆₀ alkoxy group, substituted C₃-C₁₀ cycloalkyl        group, substituted C₁-C₁₀ heterocycloalkyl group, substituted        C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀ heterocycloalkenyl        group, substituted C₆-C₆₀ aryl group, substituted C₆-C₆₀ aryloxy        group, substituted C₆-C₆₀ arylthio group, substituted C₁-C₆₀        heteroaryl group, substituted monovalent non-aromatic condensed        polycyclic group and substituted monovalent non-aromatic        condensed heteropolycyclic group may be selected from a        deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H,        —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino        group, an amidino group, a hydrazine group, a hydrazone group, a        carboxylic acid group or a salt thereof, a sulfonic acid group        or a salt thereof, a phosphoric acid group or a salt thereof, a        C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl        group, and a C₁-C₆₀ alkoxy group;    -   a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl        group, and a C₁-C₆₀ alkoxy group, each substituted with at least        one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid group or a salt thereof, a phosphoric        acid group or a salt thereof, a C₃-C₁₀ cycloalkyl group, a        C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a        C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀        aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl        group, a monovalent non-aromatic condensed polycyclic group, a        monovalent non-aromatic condensed heteropolycyclic group,        —N(Q₁₁)(Q₁₂), —B(Q₁₃)(Q₁₄), —Si(Q₁₅)(Q₁₆)(Q₁₇), and        —P(═O)(Q₁₈)(Q₁₉);    -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a        C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a        C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio        group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic        condensed polycyclic group, and a monovalent non-aromatic        condensed heteropolycyclic group;    -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a        C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a        C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio        group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic        condensed polycyclic group, and a monovalent non-aromatic        condensed heteropolycyclic group, each substituted with at least        one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid group or a salt thereof, a phosphoric        acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀        alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a        C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a        C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a        C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio        group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic        condensed polycyclic group, a monovalent non-aromatic condensed        heteropolycyclic group, —N(Q₂₁)(Q₂₂), —B(Q₂₃)(Q₂₄),        —Si(Q₂₅)(Q₂₆)(Q₂₇), and —P(═O)(Q₂₈)(Q₂₉); and    -   —N(Q₃₁)(Q₃₂), —B(Q₃₃)(Q₃₄), —Si(Q₃₅)(Q₃₆)(Q₃₇), and        —P(═O)(Q₃₈)(Q₃₉);    -   wherein Q₁ to Q₉, Q₁₁ to Q₁₉, Q₂₁ to Q₂₉ and Q₃₁ to Q₃₉ may be        each independently selected from a hydrogen, a deuterium, —F,        —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an        amino group, an amidino group, a hydrazine group, a hydrazone        group, a carboxylic acid group or a salt thereof, a sulfonic        acid group or a salt thereof, a phosphoric acid group or a salt        thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a        substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted        or unsubstituted C₂-C₆₀ alkynyl group, a substituted or        unsubstituted C₁-C₆₀ alkoxy group, a substituted or        unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or        unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or        unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted        C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀        arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl        group, a substituted or unsubstituted monovalent non-aromatic        condensed polycyclic group, and a substituted or unsubstituted        monovalent non-aromatic condensed heteropolycyclic group.

For example, L₂ in Formula 1 may be selected from groups represented byFormulae 3-1 to 3-111:

In Formulae 3-1 to 3-111,

-   -   Z₁, Z₂, Z_(1a), Z_(1b), Z_(2a), Z_(2b), Z_(2c), R_(34a),        R_(34b), and R_(34c) may be each independently selected from    -   a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a        cyano group, a nitro group, an amino group, an amidino group, a        hydrazine group, a hydrazone group, a carboxylic acid group or a        salt thereof, a sulfonic acid group or a salt thereof, a        phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl        group, and a C₁-C₂₀ alkoxy group;    -   a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted        with at least one selected from a deuterium, —F, —Cl, —Br, —I,        —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a        cyano group, a nitro group, an amino group, an amidino group, a        hydrazine group, a hydrazone group, a carboxylic acid group or a        salt thereof, a sulfonic acid group or a salt thereof, a        phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a        cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a pyridinyl group, and        a pyrimidinyl group;    -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group; and    -   a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group, each substituted with at least one        selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂,        —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro        group, an amino group, an amidino group, a hydrazine group, a        hydrazone group, a carboxylic acid group or a salt thereof, a        sulfonic acid group or a salt thereof, a phosphoric acid group        or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group,        a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a        cyclooctyl group, an adamantanyl group, a norbornanyl group, a        cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl        group, a phenyl group, a naphthyl group, a fluorenyl group, a        phenanthrenyl group, an anthracenyl group, a fluoranthenyl        group, a triphenylenyl group, a pyrenyl group, a chrysenyl        group, a pyrrolyl group, a thiophenyl group, a furanyl group, an        imidazolyl group, a pyrazolyl group, a thiazolyl group, an        isothiazolyl group, an oxazolyl group, an isoxazolyl group, a        pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a        pyridazinyl group, an isoindolyl group, an indolyl group, an        indazolyl group, a purinyl group, a quinolinyl group, an        isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl        group, a quinazolinyl group, a cinnolinyl group, a carbazolyl        group, a phenanthrolinyl group, a benzoimidazolyl group, a        benzofuranyl group, a benzothiophenyl group, an        isobenzothiazolyl group, a benzoxazolyl group, an        isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an        oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a        dibenzothiophenyl group, a benzocarbazolyl group, a        dibenzocarbazolyl group, an imidazopyridinyl group, and an        imidazopyrimidinyl group; and    -   —N(Q₁)(Q₂), —B(Q₃)(Q₄), —Si(Q₅)(Q₆)(Q₇) and —P(═O)(Q₈)(Q₉),    -   wherein Q₁ to Q₉ may be each independently selected from    -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,        —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H,        and—CD₂CDH₂;    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group; and    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group, each        substituted with at least one selected from a deuterium and a        C₁-C₁₀ alkyl group,    -   aa2 and ab2 may be each independently 1 or 2,    -   aa3 and ab3 may be each independently an integer selected from 1        to 3,    -   aa4 and ab4 may be each independently an integer selected from 1        to 4, and    -   each of * and *′ indicates a binding site to M in Formula 1.

In some embodiments, L₂ in Formula 1 may be selected from groupsrepresented by Formulae 3-1(1) to 3-1(59) and 3-111:

In Formulae 3-1(1) to 3-1(59) and 3-111,

-   -   Z₁, Z₂, Z_(1a), Z_(1b), Z_(1c), Z_(1d), Z_(2a), Z_(2b), Z_(2c),        Z_(2d), R_(34a), R_(34b), and R_(34c) may be each independently        selected from a deuterium, —F, a cyano group, a nitro group,        —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂,        —Si(Q₅)(Q₆)(Q₇), groups represented by Formulae 9-1 to 9-17, and        groups represented by Formulae 10-1 to 10-28,    -   Q₅ to Q₇ may be each independently selected from    -   —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂,        —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H,        and—CD₂CDH₂;    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group; and    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group, each        substituted with at least one selected from a deuterium and a        C₁-C₁₀ alkyl group.

In some embodiments, in Formulae 3-1(1) to 3-1(59) and 3-111,

-   -   Z₁, Z₂, Z_(1a), Z_(1b), Z_(1c), Z_(1d), Z_(2a), Z_(2b), Z_(2c),        and Z_(2d) may be each independently selected from a deuterium,        —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, —Si(Q₅)(Q₆)(Q₇), groups represented        by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1        to 10-28,    -   Q₅ to Q₇ may be each independently selected from —CH₃, —CD₃,        —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃,        —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and—CD₂CDH₂;    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group; and    -   an n-propyl group, an isopropyl group, an n-butyl group, an        isobutyl group, a sec-butyl group, a tert-butyl group, an        n-pentyl group, an isopentyl group, a sec-pentyl group, a        tert-pentyl group, a phenyl group, and a naphthyl group, each        substituted with at least one selected from a deuterium and a        C₁-C₁₀ alkyl group, but are not limited thereto.

In an embodiment, the organometallic compound may be represented byFormula 1 in which L₁ is selected from ligands represented by Formulae2A-1 to 2A-15 (for example, ligands represented by Formulae 2A(1)-1 to2A(1)-15) and L₂ is selected from ligands represented by Formulae 3-1 to3-111 (for example, a ligand represented by Formulae 3-1(1) to 3-1(59)and 3-111).

In some embodiments, the organometallic compound is not in the form ofsalt, and may be represented by Formula 1 in which M is Ir and the sumof n1 and n2 is 3; or M is Pt and the sum of n1 and n2 is 2, L₁ isselected from ligands represented by Formulae 2A-1 to 2A-15 (forexample, ligands represented by Formulae 2A(1)-1 to 2A(1)-15), and L₂ isselected from ligands represented by Formulae 3-1 to 3-111 (for example,ligands represented by Formulae 3-1(1) to 3-1(59) and 3-111).

For example, the organometallic compound represented by Formula 1 may beone of Compounds 1 to 30, but is not limited thereto:

L₁ in Formula 1 is selected from ligands represented by Formula 2A, andat least one selected from R₁₁ to R₁₄ in Formula 2A is not hydrogen.That is, an embodiment in which all of R₁₁ to R₁₄ in Formula 2A arehydrogen at the same time is excluded. While wishing not to be bound bya theory, it is understood that when R₁₁ to R₁₄ in Formula 2A aresimultaneously hydrogen, the organometallic compound represented byFormula 1 has excellent heat-resistance and degradation-resistance, andaccordingly, an organic light-emitting device including theorganometallic compound may have high efficiency and long lifespan.

In some embodiments, L₁ in Formula 1 may be selected from ligandsrepresented by Formula 2A, and b1 in Formula 2A, which indicates thenumber of *—P(═O)(R₁)(R₂), may be 1, 2, 3, or 4. That is, a benzene ringin the ligand represented by Formula 2A necessarily has *—P(═O)(R₁)(R₂),which is an electron withdrawing group, as a substituent. Thus, theorganometallic compound represented by Formula 1 may have a relativelylow highest occupied molecular orbital (HOMO) energy level (that is, aHOMO energy level having a great absolute value), thereby emitting greenlight that is shifted to a relatively shorter wavelength.

For example, the HOMO, the lowest unoccupied molecular orbital (LUMO),and triplet (T₁) energy level of some of the organometallic compoundswere evaluated by using a DFT method of Gaussian program (B3LYP,structurally optimized at the level of 6-31G(d,p)), and evaluationresults thereof are shown in Table 1.

TABLE 1 Compound No. HOMO (eV) LUMO (eV) T₁ energy level (eV)  1 −4.996−1.330 2.650  2 −4.987 −1.323 2.649  3 −5.004 −1.320 2.653  4 −5.016−1.357 2.649  5 −4.992 −1.329 2.650  6 −4.983 −1.320 2.649  7 −5.024−1.542 2.547  8 −5.002 −1.601 2.556  9 −4.993 −1.318 2.651 10 −5.007−1.410 2.613 11 −4.982 −1.414 2.632 12 −4.978 −1.365 2.649 13 −4.957−1.345 2.598 14 −4.924 −1.287 2.637 15 −4.918 −1.267 2.655 16 −4.919−1.278 2.636 17 −4.935 −1.320 2.666 18 −4.952 −1.509 2.533 19 −4.943−1.490 2.534 20 −4.938 −1.511 2.530 21 −4.963 −1.551 2.544 22 −4.978−1.515 2.537 23 −4.924 −1.287 2.637 24 −4.918 −1.267 2.655 25 −4.919−1.278 2.636 26 −4.935 −1.320 2.666 27 −4.952 −1.509 2.533 28 −4.943−1.490 2.534 29 −4.938 −1.511 2.530 30 −4.963 −1.551 2.544 B −4.848−1.187 2.632 C −4.811 −1.196 2.569 D −4.814 −1.231 2.582 Compound B

Compound C

Compound D

Referring to Table 1, it may be seen that the organometallic compoundrepresented by Formula 1 is suitable for use as a material for anorganic light-emitting device.

A method of synthesis of the organometallic compound represented byFormula 1 would be readily recognizable by one of ordinary skill in theart by referring to Synthesis Example.

Accordingly, the organometallic compound represented by Formula 1 issuitable for use as an organic layer of an organic light-emittingdevice, for example, a dopant for an emission layer in an organic layer.According to another aspect of the present disclosure, provided is anorganic light-emitting device including:

-   -   a first electrode;    -   a second electrode; and    -   an organic layer disposed between the first electrode and the        second electrode,    -   wherein the organic layer includes the emission layer, and at        least one organometallic compound represented by Formula 1.

The organic light-emitting device may have, due to the inclusion of theorganic layer including the organometallic compound represented byFormula 1, low driving voltage, high efficiency, high power, highquantum efficiency, long lifespan, and excellent color purity.

The organometallic compound represented by Formula 1 may be used betweena pair of electrodes of an organic light-emitting device. For example,the organometallic compound represented by Formula 1 may be included inthe emission layer. In this regard, the organometallic compound acts asa dopant, and the emission layer may further include a host (that is, anamount of the organometallic compound represented by Formula 1 issmaller than an amount of the host).

The term “organic layer” as used herein refers to a single layer and/ora plurality of layers disposed between the first electrode and thesecond electrode of an organic light-emitting device. The “organiclayer” may include, in addition to an organic compound, anorganometallic complex including metal.

FIG. 1 is a schematic view of an organic light-emitting device 10according to an embodiment. Hereinafter, the structure of an organiclight-emitting device according to an embodiment and a method ofmanufacturing an organic light-emitting device 10 according to anembodiment will be described in connection with FIG. 1. The organiclight-emitting device 10 includes a first electrode 11, an organic layer15, and a second electrode 19, which are sequentially stacked.

In FIG. 1, a substrate may be additionally disposed under the firstelectrode 11 or above the second electrode 19. For use as the substrate,any substrate that is used in general organic light-emitting devices maybe used, and the substrate may be a glass substrate or transparentplastic substrate, each with excellent mechanical strength, thermalstability, transparency, surface smoothness, ease of handling, andwater-resistance.

The first electrode 11 may be formed by depositing or sputtering amaterial for forming the first electrode on the substrate. The firstelectrode 11 may be an anode. The material for the first electrode 11may be selected from materials with a high work function to allow holesbe easily provided. The first electrode 11 may be a reflective electrodeor a transmissive electrode. The material for the first electrode maybe, for example, indium tin oxide (ITO), indium zinc oxide (IZO), tinoxide (SnO₂), and zinc oxide (ZnO). In some embodiments, magnesium (Mg),aluminum (Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium(Mg—In), or magnesium-silver (Mg—Ag) may be used as the material for thefirst electrode.

The first electrode 11 may have a single-layer structure or amulti-layer structure including two or more layers. For example, thefirst electrode 11 may have a three-layered structure of ITO/Ag/ITO, butthe structure of the first electrode 110 is not limited thereto.

An organic layer 15 is disposed on the first electrode 11.

The organic layer 15 may include a hole transport region, an emissionlayer, and an electron transport region.

The hole transport region may be disposed between the first electrode 11and the emission layer.

The hole transport region may include at least one selected from a holeinjection layer, a hole transport layer, an electron blocking layer, anda buffer layer.

The hole transport region may include only either a hole injection layeror a hole transport layer. In some embodiments, the hole transportregion may have a structure of hole injection layer/hole transport layeror hole injection layer/hole transport layer/electron blocking layer,which are sequentially stacked in this stated order from the firstelectrode 11.

A hole injection layer hole injection layer may be formed on the firstelectrode 11 by using various methods, such as vacuum deposition, spincoating, casting, or Langmuir-Blodgett (LB).

When a hole injection layer is formed by vacuum deposition, thedeposition conditions may vary according to a material that is used toform the hole injection layer, and the structure and thermalcharacteristics of the hole injection layer. For example, the depositionconditions may include a deposition temperature of about 100 to about500° C., a vacuum pressure of about 10⁻⁸ to about 10⁻³ torr, and adeposition rate of about 0.01 to about 100 Angstroms per second (Å/sec).However, the deposition conditions are not limited thereto.

When the hole injection layer is formed using spin coating, coatingconditions may vary according to the material used to form the holeinjection layer, and the structure and thermal properties of the holeinjection layer. For example, a coating rate may be from about 2,000revolutions per minute (rpm) to about 5,000 rpm, and a temperature atwhich a heat treatment is performed to remove a solvent after coatingmay be from about 80° C. to about 200° C. However, the coatingconditions are not limited thereto.

Conditions for a hole transport layer and an electron blocking layer maybe understood by referring to conditions for forming the hole injectionlayer.

The hole transport region may include at least one selected fromm-MTDATA, TDATA, 2-TNATA, NPB, β-NPB, TPD, Spiro-TPD, Spiro-NPB,methylated NPB, TAPC, HMTPD, 4,4′,4″-tris(N-carbazolyl)triphenylamine(TCTA), polyaniline/dodecylbenzenesulfonic acid (Pani/DBSA),poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT/PSS),polyaniline/camphor sulfonic acid (PANI/CSA),(polyaniline)/poly(4-styrenesulfonate) (Pani/PSS), a compoundrepresented by Formula 201 below, and a compound represented by Formula202 below:

Ar₁₀₁ and Ar₁₀₂ in Formula 201 may be each independently selected from

-   -   a phenylene group, a pentalenylene group, an indenylene group, a        naphthylene group, an azulenylene group, a heptalenylene group,        an acenaphthylene group, a fluorenylene group, a phenalenylene        group, a phenanthrenylene group, an anthracenylene group, a        fluoranthenylene group, a triphenylenylene group, a pyrenylene        group, a chrysenylenylene group, a naphthacenylene group, a        picenylene group, a perylenylene group, and a pentacenylene        group; and    -   a phenylene group, a pentalenylene group, an indenylene group, a        naphthylene group, an azulenylene group, a heptalenylene group,        an acenaphthylene group, a fluorenylene group, a phenalenylene        group, a phenanthrenylene group, an anthracenylene group, a        fluoranthenylene group, a triphenylenylene group, a pyrenylene        group, a chrysenylenylene group, a naphthacenylene group, a        picenylene group, a perylenylene group, and a pentacenylene        group, each substituted with at least one selected from a        deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid or a salt thereof, a phosphoric acid or        a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a        C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl        group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkyl        group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a        C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀        heteroaryl group, a monovalent non-aromatic condensed polycyclic        group, and a monovalent non-aromatic condensed heteropolycyclic        group.

In Formula 201, xa and xb may be each independently an integer of 0 to5, or 0, 1, or 2. For example, xa is 1 and xb may be 0, but xa and xbare not limited thereto.

R₁₀₁ to R₁₀₈, R₁₁₁ to R₁₁₉ and R₁₂₁ to R₁₂₄ in Formulae 201 and 202 maybe each independently selected from

-   -   a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a        cyano group, a nitro group, an amino group, an amidino group, a        hydrazine group, a hydrazone group, a carboxylic acid group or a        salt thereof, a sulfonic acid group or a salt thereof, a        phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group        (for example, a methyl group, an ethyl group, a propyl group, a        butyl group, a pentyl group, a hexyl group, and so on), and a        C₁-C₁₀ alkoxy group (for example, a methoxy group, an ethoxy        group, a propoxy group, a butoxy group, a pentoxy group, and so        on);    -   a C₁-C₁₀ alkyl group or a C₁-C₁₀ alkoxy group, each substituted        with at least one selected from a deuterium, —F, —Cl, —Br, —I, a        hydroxyl group, a cyano group, a nitro group, an amino group, an        amidino group, a hydrazine group, a hydrazone group, a        carboxylic acid group or a salt thereof, a sulfonic acid group        or a salt thereof, and a phosphoric acid group or a salt        thereof;    -   a phenyl group, a naphthyl group, an anthracenyl group, a        fluorenyl group, and a pyrenyl group; and    -   a phenyl group, a naphthyl group, an anthracenyl group, a        fluorenyl group, and a pyrenyl group, each substituted with at        least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl        group, a cyano group, a nitro group, an amino group, an amidino        group, a hydrazine group, a hydrazone group, a carboxylic acid        group or a salt thereof, a sulfonic acid group or a salt        thereof, a phosphoric acid group or a salt thereof, a C₁-C₁₀        alkyl group, and a C₁-C₁₀ alkoxy group, but they are not limited        thereto.

R₁₀₉ in Formula 201 may be selected from

-   -   a phenyl group, a naphthyl group, an anthracenyl group and a        pyridinyl group; and    -   a phenyl group, a naphthyl group, an anthracenyl group and a        pyridinyl group, each substituted with at least one selected        from a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano        group, a nitro group, an amino group, an amidino group, a        hydrazine group, a hydrazone group, a carboxylic acid group or a        salt thereof, a sulfonic acid or a salt thereof, a phosphoric        acid or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy        group, a phenyl group, a naphthyl group, an anthracenyl group,        and a pyridinyl group.

According to an embodiment, the compound represented by Formula 201 maybe represented by Formula 201A, but is not limited thereto:

-   -   wherein R₁₀₁, R₁₁₁, R₁₁₂, and R₁₀₉ in Formula 201A may be        understood by referring to the description provided herein.

For example, the compound represented by Formula 201, and the compoundrepresented by Formula 202 may include compounds HT1 to HT20 illustratedbelow, but are not limited thereto.

A thickness of the hole transport region may be in a range of about 100Angstroms (∪) to about 10,000 ∪, for example, about 100 ═ to about 1,000∪. When the hole transport region includes a hole injection layer and ahole transport layer, the thickness of the hole injection layer may bein a range of about 100 Å to about 10,000 Å, and for example, about 100Å to about 1,000 Å, and the thickness of the hole transport layer may bein a range of about 50 Å to about 2,000 Å, and for example, about 100 Åto about 1,500 Å. While not wishing to be bound by a theory, it isunderstood that when the thicknesses of the hole transport region, thehole injection layer, and the hole transport layer are within theseranges, satisfactory hole transporting characteristics may be obtainedwithout a substantial increase in driving voltage.

The hole transport region may further include, in addition to thesematerials, a charge-generation material for the improvement ofconductive properties. The charge-generation material may behomogeneously or non-homogeneously dispersed in the hole transportregion.

The charge-generation material may be, for example, a p-dopant. Thep-dopant may be one selected from a quinone derivative, a metal oxide,and a cyano group-containing compound, but embodiments are not limitedthereto. Non-limiting examples of the p-dopant are a quinone derivative,such as tetracyanoquinonedimethane (TCNQ) or2,3,5,6-tetrafluoro-tetracyano-1,4-benzoquinonedimethane (F4-TCNQ); ametal oxide, such as a tungsten oxide or a molybdenium oxide; and acyano group-containing compound, such as Compound HT-D1 below, but arenot limited thereto.

The hole transport region may include a buffer layer.

Also, the buffer layer may compensate for an optical resonance distanceaccording to a wavelength of light emitted from the emission layer, andthus, efficiency of a formed organic light-emitting device may beimproved.

Then, an emission layer (EML) may be formed on the hole transport regionby vacuum deposition, spin coating, casting, LB deposition, or the like.When the emission layer is formed by vacuum deposition or spin coating,the deposition or coating conditions may be similar to those applied toform the hole injection layer although the deposition or coatingconditions may vary according to the material that is used to form theemission layer.

Meanwhile, when the hole transport region includes an electron blockinglayer, a material for the electron blocking layer may be selected frommaterials for the hole transport region described above and materialsfor a host to be explained later. However, the material for the electronblocking layer is not limited thereto. For example, when the holetransport region includes an electron blocking layer, a material for theelectron blocking layer may be mCP, which will be explained later.

The emission layer may include a host and a dopant, and the dopant mayinclude the organometallic compound represented by Formula 1.

For example, a HOMO energy level of the host may be in a range of −5.3electron Volts (eV) to −5.8 eV,

-   -   a LUMO energy level of the host may be in a range of −1.6 eV to        −2.0 eV, and    -   a T₁ energy level of the host may be in a range of 2.7 eV to 2.9        eV.

While not wishing to be bound by a theory, it is understood that inorganic light-emitting device including an emission layer that includesa host having such ranges of the HOMO, LUMO, and T₁ energy level and theorganometallic compound represented by Formula 1 may have highefficiency, high luminance, and long lifespan obtained by efficientenergy transition from the host to the dopant.

The host may include at least one selected form TPBi, TBADN, ADN (alsoreferred to as “DNA”), CBP, CDBP, TCP, mCP, Compound H50, and CompoundH51:

In some embodiments, the host may further include a compound representedby Formula 301 below.

Ar₁₁₁ to Ar₁₁₂ in Formula 301 may be each independently selected from

-   -   a phenylene group, a naphthylene group, a phenanthrenylene        group, and a pyrenylene group; and    -   a phenylene group, a naphthylene group, a phenanthrenylene        group, and a pyrenylene group, each substituted with at least        one selected from a phenyl group, a naphthyl group, and an        anthracenyl group.

Ar₁₁₃ to Ar₁₁₆ in Formula 301 may be each independently selected from

-   -   a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a        phenanthrenyl group, and a pyrenyl group; and    -   a phenyl group, a naphthyl group, a phenanthrenyl group, and a        pyrenyl group, each substituted with at least one selected from        a phenyl group, a naphthyl group, and an anthracenyl group.

g, h, l, and j in Formula 301 may be each independently an integer of 0to 4, for example, an integer of 0, 1, or 2.

Ar₁₁₃ to Ar₁₁₆ in Formula 301 may be each independently selected from

-   -   a C₁-C₁₀ alkyl group substituted with at least one selected from        a phenyl group, a naphthyl group, and an anthracenyl group;    -   a phenyl group, a naphthyl group, an anthracenyl group, a        pyrenyl, a phenanthrenyl group, and a fluorenyl group;    -   a phenyl group, a naphthyl group, an anthracenyl group, a        pyrenyl group, a phenanthrenyl group, and a fluorenyl group,        each substituted with at least one selected from deuterium, —F,        —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an        amino group, an amidino group, a hydrazine group, a hydrazone        group, a carboxylic acid group or a salt thereof, a sulfonic        acid or a salt thereof, a phosphoric acid or a salt thereof, a        C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl        group, a C₁-C₆₀ alkoxy group, a phenyl group, a naphthyl group,        an anthracenyl group, a pyrenyl group, a phenanthrenyl group,        and a fluorenyl group; and

but embodiments are not limited thereto.

In some embodiments, the host may include a compound represented byFormula 302 below:

Ar₁₂₂ to Ar₁₂₅ in Formula 302 are the same as described in detail inconnection with Ar_(m) in Formula 301.

Ar₁₂₆ and Ar₁₂₇ in Formula 302 may be each independently a C₁-C₁₀ alkylgroup (for example, a methyl group, an ethyl group, or a propyl group).

k and l in Formula 302 may be each independently an integer of 0 to 4.For example, k and l may be 0, 1, or 2.

The compound represented by Formula 301 and the compound represented byFormula 302 may include Compounds H1 to H42 illustrated below, but arenot limited thereto.

When the organic light-emitting device is a full color organiclight-emitting device, the emission layer may be patterned into a redemission layer, a green emission layer, and a blue emission layer. Insome embodiments, due to a stack structure including a red emissionlayer, a green emission layer, and/or a blue emission layer, theemission layer may emit white light.

When the emission layer includes a host and a dopant, an amount of thedopant may be in a range of about 0.01 to about 15 parts by weight basedon 100 parts by weight of the host, but is not limited thereto.

A thickness of the emission layer may be in a range of about 100 Å toabout 1,000 Å, for example, about 200 Å to about 600 Å. While notwishing to be bound by a theory, it is understood that when thethickness of the emission layer is within this range, excellentlight-emission characteristics may be obtained without a substantialincrease in driving voltage.

Then, an electron transport region may be disposed on the emissionlayer.

The electron transport region may include at least one selected from ahole blocking layer, an electron transport layer, and an electroninjection layer.

For example, the electron transport region may have a structure of holeblocking layer/electron transport layer/electron injection layer or astructure of electron transport layer/electron injection layer, but thestructure of the electron transport region is not limited thereto. Theelectron transport layer may have a single-layered structure or amulti-layer structure including two or more different materials.

Conditions for forming the hole blocking layer, the electron transportlayer, and the electron injection layer which constitute the electrontransport region may be understood by referring to the conditions forforming the hole injection layer.

When the electron transport layer includes a hole blocking layer, thehole blocking layer may include, for example, at least one of BCP,Bphen, and Balq but is not limited thereto.

A thickness of the hole blocking layer may be in a range of about 20 Åto about 1,000 Å, for example, about 30 Å to about 300 Å. While notwishing to be bound by a theory, it is understood that when thethickness of the hole blocking layer is within these ranges, the holeblocking layer may have improved hole blocking ability without asubstantial increase in driving voltage.

The electron transport layer may further include at least one selectedfrom BCP, Bphen, Alq₃, Balq, TAZ, and NTAZ.

In some embodiments, the electron transport layer may include at leastone of ET1 and ET2, but are not limited thereto:

A thickness of the electron transport layer may be in a range of about100 Å to about 1,000 Å, for example, about 150 Å to about 500 Å. Whilenot wishing to be bound by a theory, it is understood that when thethickness of the electron transport layer is within the range describedabove, the electron transport layer may have satisfactory electrontransport characteristics without a substantial increase in drivingvoltage.

Also, the electron transport layer may further include, in addition tothe materials described above, a metal-containing material.

The metal-containing material may include a Li complex. The Li complexmay include, for example, Compound ET-D1 (lithium quinolate, LiQ) orET-D2.

The electron transport layer may include an electron injection layer(EIL) that promotes flow of electrons from the second electrode 19thereinto.

The electron injection layer may include at least one selected from,LiF, NaCl, CsF, Li₂O, BaO, and LiQ.

A thickness of the electron injection layer may be in a range of about 1Å to about 100 Å, about 3 Å to about 90 Å. While not wishing to be boundby a theory, it is understood that when the thickness of the electroninjection layer is within the range described above, the electroninjection layer may have satisfactory electron injection characteristicswithout a substantial increase in driving voltage.

The second electrode 19 is disposed on the organic layer 15. The secondelectrode 19 may be a cathode. A material for forming the secondelectrode 19 may be selected from metal, an alloy, an electricallyconductive compound, and a combination thereof, which have a relativelylow work function. For example, lithium (Li), magnesium (Mg), aluminum(Al), aluminum-lithium (Al—Li), calcium (Ca), magnesium-indium (Mg—In),or magnesium-silver (Mg—Ag) may be formed as a material for forming thesecond electrode 19. In some embodiments, to manufacture a top emissiontype light-emitting device, a transmissive electrode formed using ITO orIZO may be used as the second electrode 19.

Hereinbefore, the organic light-emitting device has been described withreference to FIG. 1, but is not limited thereto.

A C₁-C₆₀ alkyl group as used herein refers to a linear or branchedaliphatic hydrocarbon monovalent group having 1 to 60 carbon atoms.Detailed examples thereof are a methyl group, an ethyl group, a propylgroup, an isobutyl group, a sec-butyl group, a tert-butyl group, apentyl group, an iso-amyl group, and a hexyl group. A C₁-C₆₀ alkylenegroup as used herein refers to a divalent group having the samestructure as the C₁-C₆₀ alkyl group.

A C₁-C₆₀ alkoxy group as used herein refers to a monovalent grouprepresented by—OA₁₀₁ (wherein A₁₀₁ is the C₁-C₆₀ alkyl group). Detailedexamples thereof are a methoxy group, an ethoxy group, and anisopropyloxy group.

A C₂-C₆₀ alkenyl group as used herein refers to a hydrocarbon groupformed by including at least one carbon double bond in the middle or atthe terminal of the C₂-C₆₀ alkyl group. Detailed examples thereof are anethenyl group, a propenyl group, and a butenyl group. A C₂-C₆₀alkenylene group as used herein refers to a divalent group having thesame structure as the C₂-C₆₀ alkenyl group.

A C₂-C₆₀ alkynyl group as used herein refers to a hydrocarbon groupformed by including at least one carbon trip bond in the middle or atthe terminal of the C₂-C₆₀ alkyl group. Detailed examples thereof are anethynyl group, and a propynyl group. A C₂-C₆₀ alkynylene group as usedherein refers to a divalent group having the same structure as theC₂-C₆₀ alkynyl group.

A C₃-C₁₀ cycloalkyl group as used herein refers to a monovalenthydrocarbon monocyclic group having 3 to 10 carbon atoms. Detailedexamples thereof are a cyclopropyl group, a cyclobutyl group, acyclopentyl group, a cyclohexyl group, and a cycloheptyl group. A C₃-C₁₀cycloalkylene group as used herein refers to a divalent group having thesame structure as the C₃-C₁₀ cycloalkyl group.

A C₁-C₁₀ heterocycloalkyl group as used herein refers to a monovalentmonocyclic group having at least one hetero atom selected from N, O, P,and S as a ring-forming atom and 1 to 10 carbon atoms. Detailed examplesthereof are a tetrahydrofuranyl group, and a tetrahydrothiophenyl group.A C₁-C₁₀ heterocycloalkylene group as used herein refers to a divalentgroup having the same structure as the C₁-C₁₀ heterocycloalkyl group.

A C₃-C₁₀ cycloalkenyl group as used herein refers to a monovalentmonocyclic group that has 3 to 10 carbon atoms and at least one doublebond in the ring thereof and which is not aromatic. Detailed examplesthereof are a cyclopentenyl group, a cyclohexenyl group, and acycloheptenyl group. A C₃-C₁₀ cycloalkenylene group as used hereinrefers to a divalent group having the same structure as the C₃-C₁₀cycloalkenyl group.

A C₁-C₁₀ heterocycloalkenyl group as used herein refers to a monovalentmonocyclic group that has at least one hetero atom selected from N, O,P, and S as a ring-forming atom, 1 to 10 carbon atoms, and at least onedouble bond in its ring. Detailed examples of the C₁-C₁₀heterocycloalkenyl group are a 2,3-dihydrofuranyl group and a2,3-dihydrothiophenyl group. A C₁-C₁₀ heterocycloalkenylene group asused herein refers to a divalent group having the same structure as theC₁-C₁₀ heterocycloalkenyl group.

A C₆-C₆₀ aryl group as used herein refers to a monovalent group having acarbocyclic aromatic system having 6 to 60 carbon atoms, and a C₆-C₆₀arylene group as used herein refers to a divalent group having acarbocyclic aromatic system having 6 to 60 carbon atoms. Detailedexamples of the C₆-C₆₀ aryl group are a phenyl group, a naphthyl group,an anthracenyl group, a phenanthrenyl group, a pyrenyl group, and achrysenyl group. When the C₆-C₆₀ aryl group and the C₆-C₆₀ arylene groupeach include two or more rings, the rings may be fused to each other.

A C₁-C₆₀ heteroaryl group as used herein refers to a monovalent grouphaving a carbocyclic aromatic system that has at least one hetero atomselected from N, O, P, and S as a ring-forming atom, and 1 to 60 carbonatoms. A C₁-C₆₀ heteroarylene group as used herein refers to a divalentgroup having a carbocyclic aromatic system that has at least one heteroatom selected from N, O, P, and S as a ring-forming atom, and 1 to 60carbon atoms. Examples of the C₁-C₆₀ heteroaryl group are a pyridinylgroup, a pyrimidinyl group, a pyrazinyl group, a pyridazinyl group, atriazinyl group, a quinolinyl group, and an isoquinolinyl group. Whenthe C₁-C₆₀ heteroaryl group and the C₁-C₆₀ heteroarylene group eachinclude two or more rings, the rings may be fused to each other.

A C₆-C₆₀ aryloxy group as used herein indicates —OA₁₀₂ (wherein A₁₀₂ isthe C₆-C₆₀ aryl group), and a C₆-C₆₀ arylthio group as used hereinindicates —SA₁₀₃ (wherein A₁₀₃ is the C₆-C₆₀ aryl group).

A monovalent non-aromatic condensed polycyclic group as used hereinrefers to a monovalent group (for example, having 8 to 60 carbon atoms)that has two or more rings condensed to each other, only carbon atoms asa ring forming atom, and which is non-aromatic in the entire molecularstructure. A detailed example of the monovalent non-aromatic condensedpolycyclic group is a fluorenyl group. A divalent non-aromatic condensedpolycyclic group as used herein refers to a divalent group having thesame structure as the monovalent non-aromatic condensed polycyclicgroup.

A monovalent non-aromatic condensed heteropolycyclic group as usedherein refers to a monovalent group (for example, having 2 to 60 carbonatoms) that has two or more rings condensed to each other, has aheteroatom selected from N, O P, and S, other than carbon atoms, as aring forming atom, and which is non-aromatic in the entire molecularstructure. An example of the monovalent non-aromatic condensedheteropolycyclic group is a carbazolyl group. A divalent non-aromaticcondensed heteropolycyclic group as used herein refers to a divalentgroup having the same structure as the monovalent non-aromatic condensedheteropolycyclic group.

At least one of substituents of the substituted C₁-C₆₀ alkyl group,substituted C₂-C₆₀ alkenyl group, substituted C₂-C₆₀ alkynyl group,substituted C₁-C₆₀ alkoxy group, substituted C₃-C₁₀ cycloalkyl group,substituted C₁-C₁₀ heterocycloalkyl group, substituted C₃-C₁₀cycloalkenyl group, substituted C₁-C₁₀ heterocycloalkenyl group,substituted C₆-C₆₀ aryl group, substituted C₆-C₆₀ aryloxy group,substituted C₆-C₆₀ arylthio group, substituted C₁-C₆₀ heteroaryl group,substituted monovalent non-aromatic condensed polycyclic group, andsubstituted monovalent non-aromatic condensed heteropolycyclic groupused herein is selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,—CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitrogroup, an amino group, an amidino group, a hydrazine group, a hydrazonegroup, a carboxylic acid group or a salt thereof, a sulfonic acid or asalt thereof, a phosphoric acid or a salt thereof, a C₁-C₆₀ alkyl group,a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxygroup;

-   -   a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl        group, and a C₁-C₆₀ alkoxy group, each substituted with at least        one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid or a salt thereof, a phosphoric acid or        a salt thereof, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀        heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀        heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy        group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a        monovalent non-aromatic condensed polycyclic group, a monovalent        non-aromatic condensed heteropolycyclic group, —N(Q₁₁)(Q₁₂),        —B(Q₁₃)(Q₁₄), —Si(Q₁₅)(Q₁₆)(Q₁₇), and —P(═O)(Q₁₈)(Q₁₉);    -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a        C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a        C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio        group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic        condensed polycyclic group, and a monovalent non-aromatic        condensed heteropolycyclic group;    -   a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a        C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a        C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio        group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic        condensed polycyclic group, and a monovalent non-aromatic        condensed heteropolycyclic group, each substituted with at least        one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H,        —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a        nitro group, an amino group, an amidino group, a hydrazine        group, a hydrazone group, a carboxylic acid group or a salt        thereof, a sulfonic acid or a salt thereof, a phosphoric acid or        a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a        C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl        group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl        group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a        C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀        heteroaryl group, a monovalent non-aromatic condensed polycyclic        group, a monovalent non-aromatic condensed heteropolycyclic        group, —N(Q₂₁)(Q₂₂), —B(Q₂₃)(Q₂₄), —Si(Q₂₅)(Q₂₆)(Q₂₇), and        —P(═O)(Q₂₈)(Q₂₉); and    -   —N(Q₃₁)(Q₃₂), —B(Q₃₃)(Q₃₄), —Si(Q₃₅)(Q₃₆)(Q₃₇), and        —P(═O)(Q₃₈)(Q₃₉);    -   wherein Q₁ to Q₉, Q₁₁ to Q₁₉, Q₂₁ to Q₂₉ and Q₃₁ to Q₃₉ may be        each independently selected from a hydrogen, a deuterium, —F,        —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an        amino group, an amidino group, a hydrazine group, a hydrazone        group, a carboxylic acid group or a salt thereof, a sulfonic        acid or a salt thereof, a phosphoric acid or a salt thereof, a        substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted        or unsubstituted C₂-C₆₀ alkenyl group, a substituted or        unsubstituted C₂-C₆₀ alkynyl group, a substituted or        unsubstituted C₁-C₆₀ alkoxy group, a substituted or        unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or        unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or        unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or        unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted        C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀        arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl        group, a substituted or unsubstituted monovalent non-aromatic        condensed polycyclic group, and a substituted or unsubstituted        monovalent non-aromatic condensed heteropolycyclic group.

Hereinafter, a compound and an organic light-emitting device accordingto embodiments are described in detail with reference to SynthesisExample and Examples. However, the organic light-emitting device is notlimited thereto. The wording “B was used instead of A” used indescribing Synthesis Examples means that an amount of A used wasidentical to an amount of B used, in terms of a molar equivalent.

EXAMPLE Synthesis Example 1 Synthesis of Compound 1

Synthesis of Intermediate A

1.2 milliliters (mL) of THF was added to magnesium (0.48 grams (g), 20millimoles (mmol)) at a temperature of 0° C. 1,3-dibromobenzene (4.9 g,20.8 mmol) in 20 mL of THF solution was added dropwise thereto, and theresulting mixture was stirred until magnesium completely disappeared.Then, at a temperature of 0° C., diphenylphosphinic acid chloride (3.66mL, 19 mmol) was added dropwise thereto. The resulting mixture wasstirred at room temperature, and once the reaction was completed, 10%HCl was added thereto to perform hydrolysis. The reaction mixture wasextracted using dichloromethane, the organic extracts were dried withmagnesium sulfate, and the crude product obtained by removing a solventby evaporation was purified by column chromatography(dichloromethane:ethanol) to obtain Intermediate A (1.64 g, 22%). Theobtained compound was confirmed by MALDI-MS and HPLC analysis.

MALDI-TOFMS (m/z): C₁₈H₁₄BrOP (M⁺) 356.

Synthesis of Intermediate L1

To a solution of Intermediate A (6.42 g, 18 mmol) in 18 mL of THF wasadded iPrMgCl (in 2 molar (M) diethyl ether, 10.5 mL, 28 mmol) and atroom temperature. The mixture was stirred for 2 hours, followed by theaddition of Ni(dppp)Cl₂ (0.32 g, 0.6 mmol) and 2-bromo-1-methylpyridine(2.32 g, 24 mmol). The resulting mixture was stirred for 48 hours underreflux. Once the reaction was completed, a saturated ammonium chlorideaqueous solution was added thereto to quench the reaction. The organiclayer obtained by performing an extraction process twice thereon with150 mL of difluoromethane was washed twice with 6 normal (N) HCl. Theaqueous layer was neutralized and extracted with dichloromethane. Anorganic layer obtained therefrom was dried by using magnesium sulfate,and the crude product obtained by evaporating a solvent was purified bycolumn chromatography (dichloromethane:ethanol) to obtain IntermediateL1 (0.96 g, 15%). The obtained compound was confirmed by MALDI-MS andHPLC analysis.

MALDI-TOFMS (m/z): C₂₄H₂₀NOP (M⁺) 369.

Synthesis of Intermediate B

2-phenylpyridine (14.66 g, 94.44 mmol) and iridium chloride (14.8 g,41.97 mmol) were mixed with 210 mL of ethoxyethanol and 70 mL ofdistilled water. The resulting mixture was stirred under reflux for 24hours to complete the reaction. Then, the temperature was lowered toroom temperature. The resultant solid was separated by filtration, andthoroughly washed with water, methanol, and hexane in the stated order.The obtained solid was dried in a vacuum oven to obtain Intermediate B(20.2 g, 90%).

Synthesis of Intermediate C

Intermediate B (4.5 g, 4.20 mmol) was mixed with 60 mL of methylenechloride, and AgOTf (2.16 g, 8.41 mmol) dissolved in 20 mL of methanolwas added thereto. Next, while being blocked from light by using analuminum foil, the mixture was stirred at room temperature for 18 hoursto complete the reaction. The generated solid was removed by celitefiltration, and a filtrate was concentrated under reduced pressure. Theobtained solid (Intermediate C) was used in the subsequent reactionwithout purification.

Synthesis of Compound 1

Intermediate C (5 g, 7.02 mmol) and Intermediate L1 (3.24 g, 8.77 mmol)were mixed with 70 mL of ethanol, and the resulting mixture was stirredunder reflux for 18 hours to complete the reaction. Then, thetemperature was lowered to room temperature. The resulting mixture wasfiltered to separate a solid, which was then thoroughly washed withethanol and hexane. The product was purified by column chromatographywith methylene chloride and hexane at a ratio of 35:65 to obtain 1.9 g(31%) of Compound 1. The obtained product was confirmed by Mass and HPLCanalysis.

HRMS (MALDI-TOF) calcd for C₄₆H₃₅IrN₃OP: m/z 869.2147, Found: 869.2142.

Synthesis Example 2 Synthesis of Compound 2

Synthesis of Intermediate L2

1.0 g (15%) of Intermediate L2 was prepared in the same manner asIntermediate L1 in Synthesis Example 1, except that2-bromo-4-methylpyridine (2.32 g, 24 mmol) was used instead of2-bromo-1-methylpyridine.

MALDI-TOFMS (m/z): C₂₄H₂₀NOP (M+) 369.

Synthesis of Compound 2

1.8 g (29%) of Compound 2 was prepared in the same manner as Compound 1in Synthesis Example 1, except that Intermediate L2 (3.24 g, 8.77 mmol)was used instead of Intermediate L1. The obtained product was confirmedby Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₄₆H₃₅IrN₃OP: m/z 869.2147, Found: 869.2145.

Synthesis Example 3 Synthesis of Compound 13

Synthesis of Intermediate D

2-(4-(trimethylsilyl))phenylpyridine (7.05 g, 33.07 mmol) and iridiumchloride (5.18 g, 14.7 mmol) were mixed with 75 mL of ethoxyethanol and25 mL of distilled water. The mixture was stirred under reflux for 24hours to complete the reaction. Then, the temperature was lowered toroom temperature. The resultant solid was separated by filtration, andthoroughly washed with water, methanol, and hexane in this stated order.The obtained solid was dried in a vacuum oven to obtain Intermediate D(9.01 g, 90%).

Synthesis of Intermediate E

Intermediate D (2.78 g, 2.04 mmol) was mixed with 60 mL of methylenechloride, and AgOTf (1.05 g, 4.08 mmol) dissolved in 20 mL of methanolwas added thereto. Next, while being blocked from light by using analuminum foil, the mixture was stirred at room temperature for 18 hoursto complete the reaction. The generated solid was removed by celitefiltration, and the filtrate was concentrated under reduced pressure.The obtained solid (Intermediate E) was used for the subsequent reactionwithout purification.

Synthesis of Compound 13

1.1 g (28%) of Compound 13 was prepared in the same manner as Compound 1in Synthesis Example 1, except that Intermediate E (3.38 g, 3.95 mmol)was used instead of Intermediate C. The obtained product was confirmedby Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₅₂H₅₁IrN₃OPSi₂: m/z 1013.2938, Found:1013.2936.

Synthesis Example 4 Synthesis of Compound 23

Synthesis of Intermediate F

2-(5-(methylD₃))phenylpyridine (8.74 g, 33.07 mmol) and iridium chloride(7.95 g, 22.5 mmol) were mixed with 120 mL of ethoxyethanol and 40 mL ofdistilled water. The mixture was stirred under reflux for 24 hours tocomplete the reaction. The temperature was then dropped to roomtemperature. The resultant solid was separated by filtration, andthoroughly washed with water, methanol, and hexane in this stated order.The obtained solid was dried in a vacuum oven to obtain Intermediate F(11 g, 86%).

Synthesis of Intermediate G

Intermediate F (4.59 g, 4.02 mmol) was mixed with 210 mL of methylenechloride, and AgOTf (2.07 g, 8.04 mmol) dissolved in 70 mL of methanolwas added thereto. Next, while being blocked from light by using analuminum foil, the mixture was stirred at room temperature for 18 hoursto complete the reaction. The generated solid was removed by celitefiltration, and a filtrate was concentrated under reduced pressure. Theobtained solid (Intermediate G) was used for the subsequent reactionwithout purification.

Synthesis of Compound 23

2.04 g (28%) of Compound 23 was prepared in the same manner as Compound1 in Synthesis Example 1, except that Intermediate G (6.01 g, 8.06 mmol)was used instead of Intermediate C. The obtained product was confirmedby Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₄₈H₃₃D₆IrN₃OP: m/z 903.2837, Found:903.2834.

Synthesis Example 5 Synthesis of Compound 24

Synthesis of Intermediate H

Intermediate H (10.6 g, 83%) was prepared in the same manner asIntermediate F in Synthesis Example 4, except that2-(4-(methylD₃))phenylpyridine (8.74 g, 33.07 mmol) was used instead of2-(5-(methylD₃))phenylpyridine.

Synthesis of Intermediate I

Intermediate I was prepared in the same manner as Intermediate G inSynthesis Example 4, except that Compound H (8.74 g, 33.07 mmol) wasused instead of Intermediate F.

Synthesis of Compound 24

Compound 24 (2.18 g, 30%) was prepared in the same manner as Compound 1in Synthesis Example 1, except that Intermediate I (6.01 g, 8.06 mmol)was used instead of Intermediate C. The obtained product was confirmedby Mass and HPLC analysis.

HRMS (MALDI-TOF) calcd for C₄₈H₃₃D₆IrN₃OP: m/z 903.2837, Found:903.2835.

Evaluation Example 1 Evaluation on HOMO, LUMO, and Triplet (T₁) EnergyLevels

HOMO, LUMO and T₁ energy levels of Compounds 1, 2, 13, 23, and B to Dwere evaluated according to the method indicated in Table 2, and resultsthereof are shown in Table 3.

TABLE 2 HOMO energy level A potential (Volts, V) - current (Amperes, A)graph of each compound was evaluation method obtained by using cyclicvoltammetry (CV) (electrolyte: 0.1M Bu₄NClO₄/ solvent: CH₂Cl₂/electrode:3 electrode system (working electrode: GC, reference electrode: Ag/AgCl,auxiliary electrode: Pt)). Then, from reduction onset of the graph, aHOMO energy level of the compound was calculated. LUMO energy level Eachcompound was diluted at a concentration of 1 × 10⁻⁵ molar (M) inevaluation method CHCl₃, and an UV absorption spectrum thereof wasmeasured at room temperature by using a Shimadzu UV-350 spectrometer,and a LUMO energy level thereof was calculated by using an optical bandgap (Eg) from an edge of the absorption spectrum. T1 energy level Amixture of 2-methyltetrahydrofuran and each compound (each compoundevaluation method was dissolved in an amount of 1 milligram (mg) in 3cubic centimeters (cc) of toluene) was loaded into a quartz cell. Then,the resultant quartz cell was loaded into liquid nitrogen (77 Kelvins,K) and a photoluminescence spectrum thereof was measured by using adevice for measuring photoluminescence. The obtained spectrum wascompared with a photoluminescence spectrum measured at room temperature,and peaks appearing only at low temperature were analyzed to calculateT1 energy levels.

TABLE 3 HOMO (eV) LUMO (eV) Compound No. (found) (found) T₁ energy level(eV)  1 −5.100 −2.439 2.536  2 −5.091 −2.430 2.535 13 −5.060 −2.4002.485 23 −5.048 −2.388 2.523 B −5.038 −2.502 2.398 C −5.039 −2.472 2.500D −5.013 −2.493 2.480 Compound B

Compound C

Compound D

Referring to Table 3, it may be seen that absolute values of Compounds1, 2, 13, and 23 are greater than those of HOMO of Compounds B throughD.

Example 1

An ITO glass substrate was cut to a size of 50 millimeters (mm)×50mm×0.5 mm, sonicated in acetone isopropyl alcohol and pure water, eachfor 15 minutes, and washed under exposure to UV ozone for 30 minutes.

Subsequently, on the ITO (anode) glass substrate, m-MTDATA was depositedat a deposition rate of 1 Angstroms per second (Å/sec) to form a holeinjection layer having a thickness of 600 Angstroms (Å), and α-NPD wasdeposited on the hole injection layer at a deposition rate of 1 Å/sec toform a hole transport layer having a thickness of 250 Å.

Compound 1 (dopant) and CBP (host) were co-deposited on the holetransport layer at a deposition rate of 0.1 Å/sec and a deposition rateof 1 Å/sec, respectively, to form an emission layer having a thicknessof 400 Å.

BAlq was deposited on the emission layer at a deposition rate of 1 Å/secto form a hole blocking layer having a thickness of 50 Å, and Alq₃ wasdeposited on the hole blocking layer to form an electron transport layerhaving a thickness of 300 Å. Then, LiF was deposited on the electrontransport layer to form an electron injection layer having a thicknessof 10 Å, and Al was vacuum deposited on the electron injection layer toform a second electrode (cathode) having a thickness of 1,200 Å, therebycompleting the manufacture of an organic light-emitting device having astructure of ITO/m-MTDATA (600 Å)/α-NPD (250 Å)/CBP+10% (Compound 1)(400 Å)/Balq(50 Å)/Alq₃(300 Å)/LiF(10 Å)/Al(1200 Å).

Evaluation Example 2 Evaluation on Characteristics of OrganicLight-Emitting Devices

The organic light-emitting devices manufactured according to Examples 1to 4 and Comparative Examples 1 and 2 were evaluated in terms of drivingvoltage, efficiency, power, color purity, quantum efficiency, andlifespan. Results thereof are shown in Table 4. This evaluation wasperformed using a current-voltage meter (Keithley 2400) and luminancemeter (Minolta Cs-1000A). Lifespan (T₉₅, at 6000 nit) was evaluated bymeasuring the amount of time that elapsed until luminance was reduced to95% of the initial brightness of 100%.

TABLE 4 Driving Lifespan Voltage Quantum (hr) Voltage Efficiency PowerEfficiency (T₉₅, at Dopant (V) (cd/A) (Im/W) CIEx CIEy (%) 6000 nit)Example 1 Compound 1 3.6 42.6 37.2 0.306 0.598 18 40 Example 2 Compound2 3.6 41.8 36.5 0.308 0.599 18 42 Example 3 Compound 13 4.0 48.8 38.30.316 0.602 19 51 Example 4 Compound 24 4.5 45.7 31.9 0.323 0.601 19 38Comparative Compound A 3.7 37.6 32.2 0.316 0.599 18 30 Example 1Comparative Ir(ppy)₃ 6.5 40.2 19.4 0.330 0.604 18 15 Example 2

Compound A

From Table 4, it was confirmed that the organic light-emitting devicesprepared according to Examples 1 to 4 have lower driving voltage, higherefficiency, and longer lifespan than the organic light-emitting devicesprepared according to Comparative Examples 1 and 2.

The organometallic compound according to embodiments has excellentelectric characteristics and thermal stability. Accordingly, an organiclight-emitting device including the organometallic compound may haveexcellent driving voltage, current density, efficiency, power, colorpurity, and lifespan characteristics.

It should be understood that exemplary embodiments described hereinshould be considered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exemplaryembodiment should typically be considered as available for other similarfeatures or aspects in other exemplary embodiments.

While one or more exemplary embodiments have been described withreference to the figures, it will be understood by those of ordinaryskill in the art that various changes in form and details may be madetherein without departing from the spirit and scope as defined by thefollowing claims.

What is claimed is:
 1. An organometallic compound represented by Formula 1:

wherein M in Formula 1 is selected from Ir, Pt, Os, Ti, Zr, Hf, Eu, Tb, Tm, and Rh, L₁ in Formula 1 is selected from ligands represented by Formula 2A, and n1 is 1, 2, or 3, and when n1 is 2 or greater, two or more groups L₁ are identical to or different from each other, L₂ in Formula 1 is selected from a monovalent organic ligand, a divalent organic ligand, a trivalent organic ligand, and a tetravalent organic ligand, and n2 is 0, 1, 2, 3, or 4, and when n2 is 2 or greater, two or more groups L₂ are identical to or different from each other, L₁ and L₂ in Formula 1 are different from each other, R₁, R₂ and R₁₁ to R₁₅ in Formula 2A are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, —SF₅, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁)(Q₂), and —B(Q₃)(Q₄), provided that at least one selected from R₁₁ to R₁₄ in Formula 2A is not hydrogen, b1 in Formula 2A is selected from 1, 2, 3, and 4, b2 in Formula 2A is selected from 0, 1, 2, and 3, each of * and *′ in Formula 2A indicates a binding site to M in Formula 1, and at least one of substituents of the substituted C₁-C₆₀ alkyl group, substituted C₂-C₆₀ alkenyl group, substituted C₂-C₆₀ alkynyl group, substituted C₁-C₆₀ alkoxy group, substituted C₃-C₁₀ cycloalkyl group, substituted C₁-C₁₀ heterocycloalkyl group, substituted C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀ heterocycloalkenyl group, substituted C₆-C₆₀ aryl group, substituted C₆-C₆₀ aryloxy group, substituted C₆-C₆₀ arylthio group, substituted C₁-C₆₀ heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group and substituted monovalent non-aromatic condensed heteropolycyclic group is selected from: a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxy group; a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxy group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁₁)(Q₁₂), and —B(Q₁₃)(Q₁₄); a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group; a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q₂₁)(Q₂₂), and —B(Q₂₃)(Q₂₄); and —N(Q₃₁)(Q₃₂) and —B(Q₃₃)(Q₃₄), wherein Q₁ to Q₄, Q₁₁ to Q₁₄, Q₂₁ to Q₂₄, and Q₃₁ to Q₃₄ are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group.
 2. The organometallic compound of claim 1, wherein in Formula 1, M is Ir, and the sum of n1 and n2 is 3; or M is Pt, and the sum of n1 and n2 is 2, and the organometallic compound is not in the form of a salt.
 3. The organometallic compound of claim 1, wherein R₁ and R₂ in Formula 2A are each independently selected from a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl group; and a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group.
 4. The organometallic compound of claim 1, wherein R₁ and R₂ in Formula 2A are each independently selected from a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl group; and a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, an imidazopyrimidinyl group, and a 1,2,3,4-tetrahydronaphthyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group.
 5. The organometallic compound of claim 1, wherein R₁ and R₂ in Formula 2A are each independently selected from a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group and a 1,2,3,4-tetrahydronaphthyl group; and a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, and a 1,2,3,4-tetrahydronaphthyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group.
 6. The organometallic compound of claim 1, wherein R₁₁ to R₁₅ in Formula 2A are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl group, and a C₁-C₂₀ alkoxy group; a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group; a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group; and —N(Q₁)(Q₂) and —B(Q₃)(Q₄), wherein Q₁ to Q₄ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium, a C₁-C₁₀ alkyl group, and a phenyl group.
 7. The organometallic compound of claim 1, wherein R₁₁ to R₁₅ in Formula 2A are each independently selected from a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group and a pyrimidinyl group; a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group, each substituted with at least one selected from a deuterium, —F, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; and —N(Q₁)(Q₂) and —B(Q₃)(Q₄), wherein Q₁ to Q₄ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium, a C₁-C₁₀ alkyl group, and a phenyl group.
 8. The organometallic compound of claim 1, wherein R₁₁ to R₁₅ in Formula 2A are each independently selected from a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, R₁ and R₂ in Formula 2A are each independently selected from a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group; and a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group:


9. The organometallic compound of claim 1, wherein L₁ is selected from ligands represented by Formulae 2A-1 to 2A-15:

wherein R₁₁ to R₁₄ in Formulae 2A-1 to 2A-15 are each independently selected from a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl group, and a C₁-C₂₀ alkoxy group; a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group; a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group and an imidazopyrimidinyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group; and —N(Q₁)(Q₂) and —B(Q₃)(Q₄), wherein Q₁ to Q₄ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium, a C₁-C₁₀ alkyl group, and a phenyl group, and R₁, R₂, R₁₅, b1, and b2 are the same as in claim
 1. 10. The organometallic compound of claim 1, wherein L₁ in Formula 1 is selected from ligands represented by Formula 2A(1):

wherein R₁, R₂, and R₁₁ to R₁₄ in Formula 2A(1) are the same as in claim 1, and R_(15a), R_(15b), and R_(15c) are the same as R₁₅.
 11. The organometallic compound of claim 1, wherein L₁ is selected from ligands represented by Formulae 2A(1)-1 to 2A(1)-15:

wherein in Formulae 2A(1)-1 to 2A(1)-15, R₁₁ to R₁₄ are each independently selected from a deuterium, —F, a cyano group, a nitro group, —SF₅, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group, each substituted with at least one selected from a deuterium, —F, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; and —N(Q₁)(Q₂) and —B(Q₃)(Q₄), R_(15a), R_(15b), and R_(15c) are each independently selected from a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, an n-hexyl group, an iso-hexyl group, a sec-hexyl group, a tert-hexyl group, an n-heptyl group, an iso-heptyl group, a sec-heptyl group, a tert-heptyl group, an n-octyl group, an iso-octyl group, a sec-octyl group, a tert-octyl group, an n-nonyl group, an iso-nonyl group, a sec-nonyl group, a tert-nonyl group, an n-decyl group, an iso-decyl group, a sec-decyl group, a tert-decyl group, a methoxy group, an ethoxy group, a propoxy group, butoxy group, a pentoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group and a pyrimidinyl group, each substituted with at least one selected from a deuterium, —F, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a cyano group, a nitro group, a C₁-C₁₀ alkyl group, a C₁-C₁₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; and —N(Q₁)(Q₂) and —B(Q₃)(Q₄), R₁ and R₂ are each independently selected from a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group; and a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group and a carbazolyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group, and wherein Q₁ to Q₄ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium, a C₁-C₁₀ alkyl group, and a phenyl group.
 12. The organometallic compound of claim 1, wherein L₂ in Formula 1 is selected from ligands represented by Formulae 3A to 3G:

wherein in Formulae 3A to 3G, Y₁₁ to Y₁₆ are each independently selected from carbon (C) or nitrogen (N), Y₁₁ and Y₁₂ are linked to each other via a single bond or a double bond, Y₁₃ and Y₁₄ are linked to each other via a single bond or a double bond, Y₁₅ and Y₁₆ are linked to each other via a single bond or a double bond, CY₃ to CY₅ are each independently selected from a C₅-C₆₀ cyclic group and a C₂-C₆₀ heterocyclic group, a1 to a3 are each independently an integer selected from 1 to 5; A₁ is P or As; X_(11a), X_(11b), X_(12a), X_(12b), X_(13a), and X_(13b) are each independently selected from N, O, N(R₃₄), P(R₃₅)(R₃₆), and As(R₃₇)(R₃₈) (provided that X_(12a), X_(12b), X_(13a), and X_(13b) are neither N nor O); R_(33″) and R_(34″) are each independently selected from a single bond, a double bond, a substituted or unsubstituted C₁-C₅ alkylene group, a substituted or unsubstituted C₂-C₅ alkenylene group, and a substituted or unsubstituted C₆-C₁₀ arylene group; Z₁ to Z₃, R₃₁, R_(32a), R_(32b), R_(32c), R_(33a), R_(33b), R₃₄ to R₃₈, R_(35a), R_(35b), R_(35c), and R_(35d) are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁)(Q₂), —B(Q₃)(Q₄), —Si(Q₅)(Q₆)(Q₇), and —P(═O)(Q₈)(Q₉), each of * and *′ indicates a binding site to M in Formula 1, and at least one of substituents of the substituted C₁-C₅ alkylene group, substituted C₂-C₅ alkenylene group, substituted C₆-C₁₀ arylene group, substituted C₁-C₆₀ alkyl group, substituted C₂-C₆₀ alkenyl group, substituted C₂-C₆₀ alkynyl group, substituted C₁-C₆₀ alkoxy group, substituted C₃-C₁₀ cycloalkyl group, substituted C₁-C₁₀ heterocycloalkyl group, substituted C₃-C₁₀ cycloalkenyl group, substituted C₁-C₁₀ heterocycloalkenyl group, substituted C₆-C₆₀ aryl group, substituted C₆-C₆₀ aryloxy group, substituted C₆-C₆₀ arylthio group, substituted C₁-C₆₀ heteroaryl group, substituted monovalent non-aromatic condensed polycyclic group, and substituted monovalent non-aromatic condensed heteropolycyclic group is selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxy group; a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, and a C₁-C₆₀ alkoxy group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q₁₁)(Q₁₂), —B(Q₁₃)(Q₁₄), —Si(Q₁₅)(Q₁₆)(Q₁₇), and —P(═O)(Q₁₈)(Q₁₉); a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group; a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₆₀ alkyl group, a C₂-C₆₀ alkenyl group, a C₂-C₆₀ alkynyl group, a C₁-C₆₀ alkoxy group, a C₃-C₁₀ cycloalkyl group, a C₁-C₁₀ heterocycloalkyl group, a C₃-C₁₀ cycloalkenyl group, a C₁-C₁₀ heterocycloalkenyl group, a C₆-C₆₀ aryl group, a C₆-C₆₀ aryloxy group, a C₆-C₆₀ arylthio group, a C₁-C₆₀ heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —N(Q₂₁)(Q₂₂), —B(Q₂₃)(Q₂₄), —Si(Q₂₅)(Q₂₆)(Q₂₇), and —P(═O)(Q₂₈)(Q₂₉); and —N(Q₃₁)(Q₃₂), —B(Q₃₃)(Q₃₄), —Si(Q₃₅)(Q₃₆)(Q₃₇), and —P(═O)(Q₃₈)(Q₃₉), wherein Q₁ to Q₉, Q₁₁ to Q₁₉, Q₂₁ to Q₂₉, and Q₃₁ to Q₃₉ are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a substituted or unsubstituted C₁-C₆₀ alkyl group, a substituted or unsubstituted C₂-C₆₀ alkenyl group, a substituted or unsubstituted C₂-C₆₀ alkynyl group, a substituted or unsubstituted C₁-C₆₀ alkoxy group, a substituted or unsubstituted C₃-C₁₀ cycloalkyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkyl group, a substituted or unsubstituted C₃-C₁₀ cycloalkenyl group, a substituted or unsubstituted C₁-C₁₀ heterocycloalkenyl group, a substituted or unsubstituted C₆-C₆₀ aryl group, a substituted or unsubstituted C₆-C₆₀ aryloxy group, a substituted or unsubstituted C₆-C₆₀ arylthio group, a substituted or unsubstituted C₁-C₆₀ heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, and a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group.
 13. The organometallic compound of claim 1, wherein L₂ in Formula 1 is selected from ligands represented by Formulae 3-1 to 3-111:

wherein in Formulae 3-1 to 3-111, Z₁, Z₂, Z_(1a), Z_(1b), Z_(2a), Z_(2b), Z_(2c), R_(34a), R_(34b), and R_(34c) are each independently selected from a hydrogen, a deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, —SF₅, C₁-C₂₀ alkyl group, and a C₁-C₂₀ alkoxy group; a C₁-C₂₀ alkyl group and a C₁-C₂₀ alkoxy group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₁₀ alkyl group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a pyridinyl group, and a pyrimidinyl group; a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group and an imidazopyrimidinyl group; a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group and an imidazopyrimidinyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a cyclopentyl group, a cyclohexyl group, a cycloheptyl group, a cyclooctyl group, an adamantanyl group, a norbornanyl group, a cyclopentenyl group, a cyclohexenyl group, a cycloheptenyl group, a phenyl group, a naphthyl group, a fluorenyl group, a phenanthrenyl group, an anthracenyl group, a fluoranthenyl group, a triphenylenyl group, a pyrenyl group, a chrysenyl group, a pyrrolyl group, a thiophenyl group, a furanyl group, an imidazolyl group, a pyrazolyl group, a thiazolyl group, an isothiazolyl group, an oxazolyl group, an isoxazolyl group, a pyridinyl group, a pyrazinyl group, a pyrimidinyl group, a pyridazinyl group, an isoindolyl group, an indolyl group, an indazolyl group, a purinyl group, a quinolinyl group, an isoquinolinyl group, a benzoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a cinnolinyl group, a carbazolyl group, a phenanthrolinyl group, a benzoimidazolyl group, a benzofuranyl group, a benzothiophenyl group, an isobenzothiazolyl group, a benzoxazolyl group, an isobenzoxazolyl group, a triazolyl group, a tetrazolyl group, an oxadiazolyl group, a triazinyl group, a dibenzofuranyl group, a dibenzothiophenyl group, a benzocarbazolyl group, a dibenzocarbazolyl group, an imidazopyridinyl group, and an imidazopyrimidinyl group; and —N(Q₁)(Q₂), —B(Q₃)(Q₄), —Si(Q₅)(Q₆)(Q₇), and —P(═O)(Q₈)(Q₉), wherein Q₁ to Q₉ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium and a C₁-C₁₀ alkyl group, aa2 and ab2 are each independently 1 or 2, aa3 and ab3 are each independently an integer selected from 1 to 3, aa4 and ab4 are each independently an integer selected from 1 to 4, and each of * and *′ indicates a binding site to M in Formula
 1. 14. The organometallic compound of claim 1, wherein L₂ in Formula 1 is selected from ligands represented by Formulae 3-1(1) to 3-1(59) and 3-111:

wherein in Formulae 3-1(1) to 3-1(59) and 3-111, Z₁, Z₂, Z_(1a), Z_(1b), Z_(1c), Z_(1d), Z_(2a), Z_(2b), Z_(2c), Z_(2d), R_(34a), R_(34b), and R_(34c) are each independently selected from a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, —Si(Q₅)(Q₆)(Q₇), groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, and wherein Q₅ to Q₇ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium and a C₁-C₁₀ alkyl group:


15. The organometallic compound of claim 1, wherein in Formula 1, M is Ir and the sum of n1 and n2 is 3; or M is Pt and the sum of n1 and n2 is 2, the organometallic compound is not in the form of a salt, and L₁ in Formula 1 is selected from ligands represented by Formulae 2A(1)-1 to 2A(1)-15, and L₂ in Formula 1 is selected from ligands represented by Formulae 3-1(1) to 3-1(59):

wherein in Formulae 2A(1)-1 to 2A(1)-15, R₁₁ to R₁₄ are each independently selected from a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, R_(15a), R_(15b), and R_(15c) are each independently selected from a hydrogen, a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, R₁ and R₂ are each independently selected from a C₁-C₁₀ alkyl group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, and a 1,2,3,4-tetrahydronaphthyl group; and a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, a carbazolyl group, and 1,2,3,4-tetrahydronaphthalenyl group, each substituted with at least one selected from a deuterium, —F, —Cl, —Br, —I, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, a hydroxyl group, a cyano group, a nitro group, an amino group, an amidino group, a hydrazine group, a hydrazone group, a carboxylic acid group or a salt thereof, a sulfonic acid group or a salt thereof, a phosphoric acid group or a salt thereof, a C₁-C₂₀ alkyl group, a C₁-C₂₀ alkoxy group, a phenyl group, a naphthyl group, a pyridinyl group, a pyrimidinyl group, a quinolinyl group, an isoquinolinyl group, a quinoxalinyl group, a quinazolinyl group, and a carbazolyl group; and in Formula 3-1(1) to 3-1(59), Z₁, Z₂, Z_(1a), Z_(1b), Z_(1c), Z_(1d), Z_(2a), Z_(2b), Z_(2c), and Z_(2d) are each independently selected from a deuterium, —F, a cyano group, a nitro group, —SF₅, —CH₃, —CD₃, —CD₂H, —CDH₂, —CF₃, —CF₂H, —CFH₂, —Si(Q₅)(Q₆)(Q₇), groups represented by Formulae 9-1 to 9-17, and groups represented by Formulae 10-1 to 10-28, Q₅ to Q₇ are each independently selected from —CH₃, —CD₃, —CD₂H, —CDH₂, —CH₂CH₃, —CH₂CD₃, —CH₂CD₂H, —CH₂CDH₂, —CHDCH₃, —CHDCD₂H, —CHDCDH₂, —CHDCD₃, —CD₂CD₃, —CD₂CD₂H, and —CD₂CDH₂; an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group; and an n-propyl group, an isopropyl group, an n-butyl group, an isobutyl group, a sec-butyl group, a tert-butyl group, an n-pentyl group, an isopentyl group, a sec-pentyl group, a tert-pentyl group, a phenyl group, and a naphthyl group, each substituted with at least one selected from a deuterium and a C₁-C₁₀ alkyl group:


16. The organometallic compound of claim 1, wherein the organometallic compound is one of Compounds 1 to 30:


17. An organic light-emitting device comprising: a first electrode; a second electrode; and an organic layer disposed between the first electrode and the second electrode, wherein the organic layer comprises an emission layer and at least one organometallic compound of claim
 1. 18. The organic light-emitting device of claim 17, wherein the first electrode is an anode, the second electrode is a cathode, and the organic layer comprises: i) a hole transport region disposed between the first electrode and the emission layer, wherein the hole transport region comprises at least one of a hole injection layer, a hole transport layer, and an electron blocking layer, and ii) an electron transport region disposed between the emission layer and the second electrode, wherein the electron transport region comprises at least one selected from a hole blocking layer, an electron transport layer, and an electron injection layer.
 19. The organic light-emitting device of claim 17, wherein the emission layer comprises the organometallic compound of claim
 1. 20. The organic light-emitting device of claim 19, wherein the emission layer further comprises a host, a highest occupied molecular orbital energy level of the host is in a range of about −5.3 electron Volts to about −5.8 electron Volts, a lowest unoccupied molecular orbital energy level of the host is in a range of about −1.6 electron Volts to about −2.0 electron Volts, and a T₁ energy level of the host is in a range of about 2.7 electron Volts to about 2.9 electron Volts. 